diff --git a/egs/librispeech/ASR/pruned_transducer_stateless2/beam_search.py b/egs/librispeech/ASR/pruned_transducer_stateless2/beam_search.py
index f5f15808d..0fba9001e 100644
--- a/egs/librispeech/ASR/pruned_transducer_stateless2/beam_search.py
+++ b/egs/librispeech/ASR/pruned_transducer_stateless2/beam_search.py
@@ -22,7 +22,6 @@ from typing import Dict, List, Optional, Tuple, Union
 import k2
 import sentencepiece as spm
 import torch
-from model import Transducer
 
 from icefall import NgramLm, NgramLmStateCost
 from icefall.decode import Nbest, one_best_decoding
@@ -36,10 +35,11 @@ from icefall.utils import (
     get_texts,
     get_texts_with_timestamp,
 )
+from torch import nn
 
 
 def fast_beam_search_one_best(
-    model: Transducer,
+    model: nn.Module,
     decoding_graph: k2.Fsa,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
@@ -103,7 +103,7 @@ def fast_beam_search_one_best(
 
 
 def fast_beam_search_nbest_LG(
-    model: Transducer,
+    model: nn.Module,
     decoding_graph: k2.Fsa,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
@@ -229,7 +229,7 @@ def fast_beam_search_nbest_LG(
 
 
 def fast_beam_search_nbest(
-    model: Transducer,
+    model: nn.Module,
     decoding_graph: k2.Fsa,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
@@ -319,7 +319,7 @@ def fast_beam_search_nbest(
 
 
 def fast_beam_search_nbest_oracle(
-    model: Transducer,
+    model: nn.Module,
     decoding_graph: k2.Fsa,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
@@ -424,7 +424,7 @@ def fast_beam_search_nbest_oracle(
 
 
 def fast_beam_search(
-    model: Transducer,
+    model: nn.Module,
     decoding_graph: k2.Fsa,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
@@ -523,7 +523,7 @@ def fast_beam_search(
 
 
 def greedy_search(
-    model: Transducer,
+    model: nn.Module,
     encoder_out: torch.Tensor,
     max_sym_per_frame: int,
     return_timestamps: bool = False,
@@ -623,7 +623,7 @@ def greedy_search(
 
 
 def greedy_search_batch(
-    model: Transducer,
+    model: nn.Module,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
     return_timestamps: bool = False,
@@ -914,7 +914,7 @@ def get_hyps_shape(hyps: List[HypothesisList]) -> k2.RaggedShape:
 
 
 def modified_beam_search(
-    model: Transducer,
+    model: nn.Module,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
     beam: int = 4,
@@ -1083,7 +1083,7 @@ def modified_beam_search(
 
 
 def modified_beam_search_lm_rescore(
-    model: Transducer,
+    model: nn.Module,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
     LM: LmScorer,
@@ -1281,7 +1281,7 @@ def modified_beam_search_lm_rescore(
 
 
 def modified_beam_search_lm_rescore_LODR(
-    model: Transducer,
+    model: nn.Module,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
     LM: LmScorer,
@@ -1497,7 +1497,7 @@ def modified_beam_search_lm_rescore_LODR(
 
 
 def _deprecated_modified_beam_search(
-    model: Transducer,
+    model: nn.Module,
     encoder_out: torch.Tensor,
     beam: int = 4,
     return_timestamps: bool = False,
@@ -1622,7 +1622,7 @@ def _deprecated_modified_beam_search(
 
 
 def beam_search(
-    model: Transducer,
+    model: nn.Module,
     encoder_out: torch.Tensor,
     beam: int = 4,
     temperature: float = 1.0,
@@ -1782,7 +1782,7 @@ def beam_search(
 
 
 def fast_beam_search_with_nbest_rescoring(
-    model: Transducer,
+    model: nn.Module,
     decoding_graph: k2.Fsa,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
@@ -1942,7 +1942,7 @@ def fast_beam_search_with_nbest_rescoring(
 
 
 def fast_beam_search_with_nbest_rnn_rescoring(
-    model: Transducer,
+    model: nn.Module,
     decoding_graph: k2.Fsa,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
@@ -2133,7 +2133,7 @@ def fast_beam_search_with_nbest_rnn_rescoring(
 
 
 def modified_beam_search_ngram_rescoring(
-    model: Transducer,
+    model: nn.Module,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
     ngram_lm: NgramLm,
@@ -2297,7 +2297,7 @@ def modified_beam_search_ngram_rescoring(
 
 
 def modified_beam_search_LODR(
-    model: Transducer,
+    model: nn.Module,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
     LODR_lm: NgramLm,
@@ -2568,7 +2568,7 @@ def modified_beam_search_LODR(
 
 
 def modified_beam_search_lm_shallow_fusion(
-    model: Transducer,
+    model: nn.Module,
     encoder_out: torch.Tensor,
     encoder_out_lens: torch.Tensor,
     LM: LmScorer,
diff --git a/egs/librispeech/ASR/zipformer/ctc_decode.py b/egs/librispeech/ASR/zipformer/ctc_decode.py
index 9efca977f..4db50b981 100755
--- a/egs/librispeech/ASR/zipformer/ctc_decode.py
+++ b/egs/librispeech/ASR/zipformer/ctc_decode.py
@@ -20,49 +20,57 @@
 # limitations under the License.
 """
 Usage:
+
 (1) ctc-decoding
-./pruned_transducer_stateless7_ctc/ctc_decode.py \
+./zipformer/ctc_decode.py \
     --epoch 30 \
     --avg 15 \
-    --exp-dir ./pruned_transducer_stateless7_ctc/exp \
+    --exp-dir ./zipformer/exp \
+    --use-ctc 1 \
     --max-duration 600 \
     --decoding-method ctc-decoding
 
 (2) 1best
-./pruned_transducer_stateless7_ctc/ctc_decode.py \
+./zipformer/ctc_decode.py \
     --epoch 30 \
     --avg 15 \
-    --exp-dir ./pruned_transducer_stateless7_ctc/exp \
+    --exp-dir ./zipformer/exp \
+    --use-ctc 1 \
     --max-duration 600 \
-    --hlg-scale 0.8 \
+    --hlg-scale 0.6 \
     --decoding-method 1best
 
 (3) nbest
-./pruned_transducer_stateless7_ctc/ctc_decode.py \
+./zipformer/ctc_decode.py \
     --epoch 30 \
     --avg 15 \
-    --exp-dir ./pruned_transducer_stateless7_ctc/exp \
+    --exp-dir ./zipformer/exp \
+    --use-ctc 1 \
     --max-duration 600 \
-    --hlg-scale 0.8 \
+    --hlg-scale 0.6 \
     --decoding-method nbest
 
 (4) nbest-rescoring
-./pruned_transducer_stateless7_ctc/ctc_decode.py \
+./zipformer/ctc_decode.py \
     --epoch 30 \
     --avg 15 \
-    --exp-dir ./pruned_transducer_stateless7_ctc/exp \
+    --exp-dir ./zipformer/exp \
+    --use-ctc 1 \
     --max-duration 600 \
-    --hlg-scale 0.8 \
+    --hlg-scale 0.6 \
+    --nbest-scale 1.0 \
     --lm-dir data/lm \
     --decoding-method nbest-rescoring
 
 (5) whole-lattice-rescoring
-./pruned_transducer_stateless7_ctc/ctc_decode.py \
+./zipformer/ctc_decode.py \
     --epoch 30 \
     --avg 15 \
-    --exp-dir ./pruned_transducer_stateless7_ctc/exp \
+    --exp-dir ./zipformer/exp \
+    --use-ctc 1 \
     --max-duration 600 \
-    --hlg-scale 0.8 \
+    --hlg-scale 0.6 \
+    --nbest-scale 1.0 \
     --lm-dir data/lm \
     --decoding-method whole-lattice-rescoring
 """
@@ -156,7 +164,7 @@ def get_parser():
     parser.add_argument(
         "--exp-dir",
         type=str,
-        default="pruned_transducer_stateless7_ctc/exp",
+        default="zipformer/exp",
         help="The experiment dir",
     )
 
@@ -220,7 +228,7 @@ def get_parser():
     parser.add_argument(
         "--nbest-scale",
         type=float,
-        default=0.5,
+        default=1.0,
         help="""The scale to be applied to `lattice.scores`.
         It's needed if you use any kinds of n-best based rescoring.
         Used only when "method" is one of the following values:
@@ -232,7 +240,7 @@ def get_parser():
     parser.add_argument(
         "--hlg-scale",
         type=float,
-        default=0.8,
+        default=0.6,
         help="""The scale to be applied to `hlg.scores`.
         """,
     )
diff --git a/egs/librispeech/ASR/zipformer/jit_pretrained_ctc.py b/egs/librispeech/ASR/zipformer/jit_pretrained_ctc.py
new file mode 100755
index 000000000..15423b449
--- /dev/null
+++ b/egs/librispeech/ASR/zipformer/jit_pretrained_ctc.py
@@ -0,0 +1,434 @@
+#!/usr/bin/env python3
+# Copyright      2022-2023  Xiaomi Corp.        (authors: Fangjun Kuang,
+#                                                         Zengwei Yao)
+#
+# See ../../../../LICENSE for clarification regarding multiple authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+This script loads a checkpoint and uses it to decode waves.
+You can generate the checkpoint with the following command:
+
+- For non-streaming model:
+
+./zipformer/export.py \
+  --exp-dir ./zipformer/exp \
+  --use-ctc 1 \
+  --bpe-model data/lang_bpe_500/bpe.model \
+  --epoch 30 \
+  --avg 9 \
+  --jit 1
+
+- For streaming model:
+
+./zipformer/export.py \
+  --exp-dir ./zipformer/exp \
+  --use-ctc 1 \
+  --causal 1 \
+  --bpe-model data/lang_bpe_500/bpe.model \
+  --epoch 30 \
+  --avg 9 \
+  --jit 1
+
+Usage of this script:
+
+(1) ctc-decoding
+./zipformer/jit_pretrained_ctc.py \
+  --model-filename ./zipformer/exp/jit_script.pt \
+  --bpe-model data/lang_bpe_500/bpe.model \
+  --method ctc-decoding \
+  --sample-rate 16000 \
+  /path/to/foo.wav \
+  /path/to/bar.wav
+
+(2) 1best
+./zipformer/jit_pretrained_ctc.py \
+  --model-filename ./zipformer/exp/jit_script.pt \
+  --HLG data/lang_bpe_500/HLG.pt \
+  --words-file data/lang_bpe_500/words.txt  \
+  --method 1best \
+  --sample-rate 16000 \
+  /path/to/foo.wav \
+  /path/to/bar.wav
+
+(3) nbest-rescoring
+./zipformer/jit_pretrained_ctc.py \
+  --model-filename ./zipformer/exp/jit_script.pt \
+  --HLG data/lang_bpe_500/HLG.pt \
+  --words-file data/lang_bpe_500/words.txt  \
+  --G data/lm/G_4_gram.pt \
+  --method nbest-rescoring \
+  --sample-rate 16000 \
+  /path/to/foo.wav \
+  /path/to/bar.wav
+
+(4) whole-lattice-rescoring
+./zipformer/jit_pretrained_ctc.py \
+  --model-filename ./zipformer/exp/jit_script.pt \
+  --HLG data/lang_bpe_500/HLG.pt \
+  --words-file data/lang_bpe_500/words.txt  \
+  --G data/lm/G_4_gram.pt \
+  --method whole-lattice-rescoring \
+  --sample-rate 16000 \
+  /path/to/foo.wav \
+  /path/to/bar.wav
+"""
+
+import argparse
+import logging
+import math
+from typing import List
+
+import k2
+import kaldifeat
+import sentencepiece as spm
+import torch
+import torchaudio
+from ctc_decode import get_decoding_params
+from torch.nn.utils.rnn import pad_sequence
+from train import get_params
+
+from icefall.decode import (
+    get_lattice,
+    one_best_decoding,
+    rescore_with_n_best_list,
+    rescore_with_whole_lattice,
+)
+from icefall.utils import get_texts
+
+
+def get_parser():
+    parser = argparse.ArgumentParser(
+        formatter_class=argparse.ArgumentDefaultsHelpFormatter
+    )
+
+    parser.add_argument(
+        "--model-filename",
+        type=str,
+        required=True,
+        help="Path to the torchscript model.",
+    )
+
+    parser.add_argument(
+        "--words-file",
+        type=str,
+        help="""Path to words.txt.
+        Used only when method is not ctc-decoding.
+        """,
+    )
+
+    parser.add_argument(
+        "--HLG",
+        type=str,
+        help="""Path to HLG.pt.
+        Used only when method is not ctc-decoding.
+        """,
+    )
+
+    parser.add_argument(
+        "--bpe-model",
+        type=str,
+        help="""Path to bpe.model.
+        Used only when method is ctc-decoding.
+        """,
+    )
+
+    parser.add_argument(
+        "--method",
+        type=str,
+        default="1best",
+        help="""Decoding method.
+        Possible values are:
+        (0) ctc-decoding - Use CTC decoding. It uses a sentence
+            piece model, i.e., lang_dir/bpe.model, to convert
+            word pieces to words. It needs neither a lexicon
+            nor an n-gram LM.
+        (1) 1best - Use the best path as decoding output. Only
+            the transformer encoder output is used for decoding.
+            We call it HLG decoding.
+        (2) nbest-rescoring. Extract n paths from the decoding lattice,
+            rescore them with an LM, the path with
+            the highest score is the decoding result.
+            We call it HLG decoding + n-gram LM rescoring.
+        (3) whole-lattice-rescoring - Use an LM to rescore the
+            decoding lattice and then use 1best to decode the
+            rescored lattice.
+            We call it HLG decoding + n-gram LM rescoring.
+        """,
+    )
+
+    parser.add_argument(
+        "--G",
+        type=str,
+        help="""An LM for rescoring.
+        Used only when method is
+        whole-lattice-rescoring or nbest-rescoring.
+        It's usually a 4-gram LM.
+        """,
+    )
+
+    parser.add_argument(
+        "--num-paths",
+        type=int,
+        default=100,
+        help="""
+        Used only when method is attention-decoder.
+        It specifies the size of n-best list.""",
+    )
+
+    parser.add_argument(
+        "--ngram-lm-scale",
+        type=float,
+        default=1.3,
+        help="""
+        Used only when method is whole-lattice-rescoring and nbest-rescoring.
+        It specifies the scale for n-gram LM scores.
+        (Note: You need to tune it on a dataset.)
+        """,
+    )
+
+    parser.add_argument(
+        "--nbest-scale",
+        type=float,
+        default=1.0,
+        help="""
+        Used only when method is nbest-rescoring.
+        It specifies the scale for lattice.scores when
+        extracting n-best lists. A smaller value results in
+        more unique number of paths with the risk of missing
+        the best path.
+        """,
+    )
+
+    parser.add_argument(
+        "--num-classes",
+        type=int,
+        default=500,
+        help="""
+        Vocab size in the BPE model.
+        """,
+    )
+
+    parser.add_argument(
+        "--sample-rate",
+        type=int,
+        default=16000,
+        help="The sample rate of the input sound file",
+    )
+
+    parser.add_argument(
+        "sound_files",
+        type=str,
+        nargs="+",
+        help="The input sound file(s) to transcribe. "
+        "Supported formats are those supported by torchaudio.load(). "
+        "For example, wav and flac are supported. "
+        "The sample rate has to be 16kHz.",
+    )
+
+    return parser
+
+
+def read_sound_files(
+    filenames: List[str], expected_sample_rate: float = 16000
+) -> List[torch.Tensor]:
+    """Read a list of sound files into a list 1-D float32 torch tensors.
+    Args:
+      filenames:
+        A list of sound filenames.
+      expected_sample_rate:
+        The expected sample rate of the sound files.
+    Returns:
+      Return a list of 1-D float32 torch tensors.
+    """
+    ans = []
+    for f in filenames:
+        wave, sample_rate = torchaudio.load(f)
+        assert (
+            sample_rate == expected_sample_rate
+        ), f"Expected sample rate: {expected_sample_rate}. Given: {sample_rate}"
+        # We use only the first channel
+        ans.append(wave[0])
+    return ans
+
+
+@torch.no_grad()
+def main():
+    parser = get_parser()
+    args = parser.parse_args()
+
+    params = get_params()
+    # add decoding params
+    params.update(get_decoding_params())
+    params.update(vars(args))
+
+    logging.info(f"{params}")
+
+    device = torch.device("cpu")
+    if torch.cuda.is_available():
+        device = torch.device("cuda", 0)
+
+    logging.info(f"device: {device}")
+
+    model = torch.jit.load(args.model_filename)
+    model.to(device)
+    model.eval()
+
+    logging.info("Constructing Fbank computer")
+    opts = kaldifeat.FbankOptions()
+    opts.device = device
+    opts.frame_opts.dither = 0
+    opts.frame_opts.snip_edges = False
+    opts.frame_opts.samp_freq = params.sample_rate
+    opts.mel_opts.num_bins = params.feature_dim
+
+    fbank = kaldifeat.Fbank(opts)
+
+    logging.info(f"Reading sound files: {params.sound_files}")
+    waves = read_sound_files(
+        filenames=params.sound_files, expected_sample_rate=params.sample_rate
+    )
+    waves = [w.to(device) for w in waves]
+
+    logging.info("Decoding started")
+    features = fbank(waves)
+    feature_lengths = [f.size(0) for f in features]
+
+    features = pad_sequence(features, batch_first=True, padding_value=math.log(1e-10))
+    feature_lengths = torch.tensor(feature_lengths, device=device)
+
+    encoder_out, encoder_out_lens = model.encoder(features, feature_lengths)
+    ctc_output = model.ctc_output(encoder_out)  # (N, T, C)
+
+    batch_size = ctc_output.shape[0]
+    supervision_segments = torch.tensor(
+        [
+            [i, 0, feature_lengths[i].item() // params.subsampling_factor]
+            for i in range(batch_size)
+        ],
+        dtype=torch.int32,
+    )
+
+    if params.method == "ctc-decoding":
+        logging.info("Use CTC decoding")
+        bpe_model = spm.SentencePieceProcessor()
+        bpe_model.load(params.bpe_model)
+        max_token_id = params.num_classes - 1
+
+        H = k2.ctc_topo(
+            max_token=max_token_id,
+            modified=False,
+            device=device,
+        )
+
+        lattice = get_lattice(
+            nnet_output=ctc_output,
+            decoding_graph=H,
+            supervision_segments=supervision_segments,
+            search_beam=params.search_beam,
+            output_beam=params.output_beam,
+            min_active_states=params.min_active_states,
+            max_active_states=params.max_active_states,
+            subsampling_factor=params.subsampling_factor,
+        )
+
+        best_path = one_best_decoding(
+            lattice=lattice, use_double_scores=params.use_double_scores
+        )
+        token_ids = get_texts(best_path)
+        hyps = bpe_model.decode(token_ids)
+        hyps = [s.split() for s in hyps]
+    elif params.method in [
+        "1best",
+        "nbest-rescoring",
+        "whole-lattice-rescoring",
+    ]:
+        logging.info(f"Loading HLG from {params.HLG}")
+        HLG = k2.Fsa.from_dict(torch.load(params.HLG, map_location="cpu"))
+        HLG = HLG.to(device)
+        if not hasattr(HLG, "lm_scores"):
+            # For whole-lattice-rescoring and attention-decoder
+            HLG.lm_scores = HLG.scores.clone()
+
+        if params.method in [
+            "nbest-rescoring",
+            "whole-lattice-rescoring",
+        ]:
+            logging.info(f"Loading G from {params.G}")
+            G = k2.Fsa.from_dict(torch.load(params.G, map_location="cpu"))
+            G = G.to(device)
+            if params.method == "whole-lattice-rescoring":
+                # Add epsilon self-loops to G as we will compose
+                # it with the whole lattice later
+                G = k2.add_epsilon_self_loops(G)
+                G = k2.arc_sort(G)
+
+            # G.lm_scores is used to replace HLG.lm_scores during
+            # LM rescoring.
+            G.lm_scores = G.scores.clone()
+
+        lattice = get_lattice(
+            nnet_output=ctc_output,
+            decoding_graph=HLG,
+            supervision_segments=supervision_segments,
+            search_beam=params.search_beam,
+            output_beam=params.output_beam,
+            min_active_states=params.min_active_states,
+            max_active_states=params.max_active_states,
+            subsampling_factor=params.subsampling_factor,
+        )
+
+        if params.method == "1best":
+            logging.info("Use HLG decoding")
+            best_path = one_best_decoding(
+                lattice=lattice, use_double_scores=params.use_double_scores
+            )
+        if params.method == "nbest-rescoring":
+            logging.info("Use HLG decoding + LM rescoring")
+            best_path_dict = rescore_with_n_best_list(
+                lattice=lattice,
+                G=G,
+                num_paths=params.num_paths,
+                lm_scale_list=[params.ngram_lm_scale],
+                nbest_scale=params.nbest_scale,
+            )
+            best_path = next(iter(best_path_dict.values()))
+        elif params.method == "whole-lattice-rescoring":
+            logging.info("Use HLG decoding + LM rescoring")
+            best_path_dict = rescore_with_whole_lattice(
+                lattice=lattice,
+                G_with_epsilon_loops=G,
+                lm_scale_list=[params.ngram_lm_scale],
+            )
+            best_path = next(iter(best_path_dict.values()))
+
+        hyps = get_texts(best_path)
+        word_sym_table = k2.SymbolTable.from_file(params.words_file)
+        hyps = [[word_sym_table[i] for i in ids] for ids in hyps]
+    else:
+        raise ValueError(f"Unsupported decoding method: {params.method}")
+
+    s = "\n"
+    for filename, hyp in zip(params.sound_files, hyps):
+        words = " ".join(hyp)
+        s += f"{filename}:\n{words}\n\n"
+    logging.info(s)
+
+    logging.info("Decoding Done")
+
+
+if __name__ == "__main__":
+    formatter = "%(asctime)s %(levelname)s [%(filename)s:%(lineno)d] %(message)s"
+
+    logging.basicConfig(format=formatter, level=logging.INFO)
+    main()
diff --git a/egs/librispeech/ASR/zipformer/model.py b/egs/librispeech/ASR/zipformer/model.py
index 42a6dccb7..8d8ec8231 100644
--- a/egs/librispeech/ASR/zipformer/model.py
+++ b/egs/librispeech/ASR/zipformer/model.py
@@ -27,191 +27,6 @@ from icefall.utils import add_sos, make_pad_mask
 from scaling import ScaledLinear
 
 
-class Transducer(nn.Module):
-    """It implements https://arxiv.org/pdf/1211.3711.pdf
-    "Sequence Transduction with Recurrent Neural Networks"
-    """
-
-    def __init__(
-        self,
-        encoder_embed: nn.Module,
-        encoder: EncoderInterface,
-        decoder: nn.Module,
-        joiner: nn.Module,
-        encoder_dim: int,
-        decoder_dim: int,
-        joiner_dim: int,  # TODO: remove it
-        vocab_size: int,
-    ):
-        """
-        Args:
-          encoder_embed:
-            It is a Convolutional 2D subsampling module. It converts
-            an input of shape (N, T, idim) to an output of of shape
-            (N, T', odim), where T' = (T-3)//2-2 = (T-7)//2.
-          encoder:
-            It is the transcription network in the paper. Its accepts
-            two inputs: `x` of (N, T, encoder_dim) and `x_lens` of shape (N,).
-            It returns two tensors: `logits` of shape (N, T, encoder_dm) and
-            `logit_lens` of shape (N,).
-          decoder:
-            It is the prediction network in the paper. Its input shape
-            is (N, U) and its output shape is (N, U, decoder_dim).
-            It should contain one attribute: `blank_id`.
-          joiner:
-            It has two inputs with shapes: (N, T, encoder_dim) and (N, U, decoder_dim).
-            Its output shape is (N, T, U, vocab_size). Note that its output contains
-            unnormalized probs, i.e., not processed by log-softmax.
-        """
-        super().__init__()
-        assert isinstance(encoder, EncoderInterface), type(encoder)
-        assert hasattr(decoder, "blank_id")
-
-        self.encoder_embed = encoder_embed
-        self.encoder = encoder
-        self.decoder = decoder
-        self.joiner = joiner
-
-        self.simple_am_proj = ScaledLinear(encoder_dim, vocab_size, initial_scale=0.25)
-        self.simple_lm_proj = ScaledLinear(decoder_dim, vocab_size, initial_scale=0.25)
-
-    def forward(
-        self,
-        x: torch.Tensor,
-        x_lens: torch.Tensor,
-        y: k2.RaggedTensor,
-        prune_range: int = 5,
-        am_scale: float = 0.0,
-        lm_scale: float = 0.0,
-    ) -> torch.Tensor:
-        """
-        Args:
-          x:
-            A 3-D tensor of shape (N, T, C).
-          x_lens:
-            A 1-D tensor of shape (N,). It contains the number of frames in `x`
-            before padding.
-          y:
-            A ragged tensor with 2 axes [utt][label]. It contains labels of each
-            utterance.
-          prune_range:
-            The prune range for rnnt loss, it means how many symbols(context)
-            we are considering for each frame to compute the loss.
-          am_scale:
-            The scale to smooth the loss with am (output of encoder network)
-            part
-          lm_scale:
-            The scale to smooth the loss with lm (output of predictor network)
-            part
-        Returns:
-          Return the transducer loss.
-
-        Note:
-           Regarding am_scale & lm_scale, it will make the loss-function one of
-           the form:
-              lm_scale * lm_probs + am_scale * am_probs +
-              (1-lm_scale-am_scale) * combined_probs
-        """
-        assert x.ndim == 3, x.shape
-        assert x_lens.ndim == 1, x_lens.shape
-        assert y.num_axes == 2, y.num_axes
-
-        assert x.size(0) == x_lens.size(0) == y.dim0
-
-        # logging.info(f"Memory allocated at entry: {torch.cuda.memory_allocated() // 1000000}M")
-        x, x_lens = self.encoder_embed(x, x_lens)
-        # logging.info(f"Memory allocated after encoder_embed: {torch.cuda.memory_allocated() // 1000000}M")
-
-        src_key_padding_mask = make_pad_mask(x_lens)
-        x = x.permute(1, 0, 2)  # (N, T, C) -> (T, N, C)
-
-        encoder_out, x_lens = self.encoder(x, x_lens, src_key_padding_mask)
-        encoder_out = encoder_out.permute(1, 0, 2)  # (T, N, C) ->(N, T, C)
-
-        assert torch.all(x_lens > 0)
-
-        # Now for the decoder, i.e., the prediction network
-        row_splits = y.shape.row_splits(1)
-        y_lens = row_splits[1:] - row_splits[:-1]
-
-        blank_id = self.decoder.blank_id
-        sos_y = add_sos(y, sos_id=blank_id)
-
-        # sos_y_padded: [B, S + 1], start with SOS.
-        sos_y_padded = sos_y.pad(mode="constant", padding_value=blank_id)
-
-        # decoder_out: [B, S + 1, decoder_dim]
-        decoder_out = self.decoder(sos_y_padded)
-
-        # Note: y does not start with SOS
-        # y_padded : [B, S]
-        y_padded = y.pad(mode="constant", padding_value=0)
-
-        y_padded = y_padded.to(torch.int64)
-        boundary = torch.zeros(
-            (encoder_out.size(0), 4),
-            dtype=torch.int64,
-            device=encoder_out.device,
-        )
-        boundary[:, 2] = y_lens
-        boundary[:, 3] = x_lens
-
-        lm = self.simple_lm_proj(decoder_out)
-        am = self.simple_am_proj(encoder_out)
-
-        # if self.training and random.random() < 0.25:
-        #    lm = penalize_abs_values_gt(lm, 100.0, 1.0e-04)
-        # if self.training and random.random() < 0.25:
-        #    am = penalize_abs_values_gt(am, 30.0, 1.0e-04)
-
-        with torch.cuda.amp.autocast(enabled=False):
-            simple_loss, (px_grad, py_grad) = k2.rnnt_loss_smoothed(
-                lm=lm.float(),
-                am=am.float(),
-                symbols=y_padded,
-                termination_symbol=blank_id,
-                lm_only_scale=lm_scale,
-                am_only_scale=am_scale,
-                boundary=boundary,
-                reduction="sum",
-                return_grad=True,
-            )
-
-        # ranges : [B, T, prune_range]
-        ranges = k2.get_rnnt_prune_ranges(
-            px_grad=px_grad,
-            py_grad=py_grad,
-            boundary=boundary,
-            s_range=prune_range,
-        )
-
-        # am_pruned : [B, T, prune_range, encoder_dim]
-        # lm_pruned : [B, T, prune_range, decoder_dim]
-        am_pruned, lm_pruned = k2.do_rnnt_pruning(
-            am=self.joiner.encoder_proj(encoder_out),
-            lm=self.joiner.decoder_proj(decoder_out),
-            ranges=ranges,
-        )
-
-        # logits : [B, T, prune_range, vocab_size]
-
-        # project_input=False since we applied the decoder's input projections
-        # prior to do_rnnt_pruning (this is an optimization for speed).
-        logits = self.joiner(am_pruned, lm_pruned, project_input=False)
-
-        with torch.cuda.amp.autocast(enabled=False):
-            pruned_loss = k2.rnnt_loss_pruned(
-                logits=logits.float(),
-                symbols=y_padded,
-                ranges=ranges,
-                termination_symbol=blank_id,
-                boundary=boundary,
-                reduction="sum",
-            )
-
-        return (simple_loss, pruned_loss)
-
-
 class AsrModel(nn.Module):
     def __init__(
         self,
diff --git a/egs/librispeech/ASR/zipformer/pretrained.py b/egs/librispeech/ASR/zipformer/pretrained.py
index b817a6b57..c0c898f4b 100755
--- a/egs/librispeech/ASR/zipformer/pretrained.py
+++ b/egs/librispeech/ASR/zipformer/pretrained.py
@@ -120,7 +120,6 @@ from beam_search import (
     greedy_search_batch,
     modified_beam_search,
 )
-from icefall.utils import make_pad_mask
 from torch.nn.utils.rnn import pad_sequence
 from train import add_model_arguments, get_params, get_model
 
@@ -318,15 +317,7 @@ def main():
     feature_lengths = torch.tensor(feature_lengths, device=device)
 
     # model forward
-    x, x_lens = model.encoder_embed(features, feature_lengths)
-
-    src_key_padding_mask = make_pad_mask(x_lens)
-    x = x.permute(1, 0, 2)  # (N, T, C) -> (T, N, C)
-
-    encoder_out, encoder_out_lens = model.encoder(
-        x, x_lens, src_key_padding_mask
-    )
-    encoder_out = encoder_out.permute(1, 0, 2)  # (T, N, C) ->(N, T, C)
+    encoder_out, encoder_out_lens = model.forward_encoder(features, feature_lengths)
 
     hyps = []
     msg = f"Using {params.method}"
diff --git a/egs/librispeech/ASR/zipformer/pretrained_ctc.py b/egs/librispeech/ASR/zipformer/pretrained_ctc.py
new file mode 100755
index 000000000..10abb0a32
--- /dev/null
+++ b/egs/librispeech/ASR/zipformer/pretrained_ctc.py
@@ -0,0 +1,453 @@
+#!/usr/bin/env python3
+# Copyright      2022-2023  Xiaomi Corp.        (authors: Fangjun Kuang,
+#                                                         Zengwei Yao)
+#
+# See ../../../../LICENSE for clarification regarding multiple authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+This script loads a checkpoint and uses it to decode waves.
+You can generate the checkpoint with the following command:
+
+- For non-streaming model:
+
+./zipformer/export.py \
+  --exp-dir ./zipformer/exp \
+  --use-ctc 1 \
+  --bpe-model data/lang_bpe_500/bpe.model \
+  --epoch 30 \
+  --avg 9
+
+- For streaming model:
+
+./zipformer/export.py \
+  --exp-dir ./zipformer/exp \
+  --use-ctc 1 \
+  --causal 1 \
+  --bpe-model data/lang_bpe_500/bpe.model \
+  --epoch 30 \
+  --avg 9
+
+Usage of this script:
+
+(1) ctc-decoding
+./zipformer/pretrained_ctc.py \
+  --checkpoint ./zipformer/exp/pretrained.pt \
+  --bpe-model data/lang_bpe_500/bpe.model \
+  --method ctc-decoding \
+  --sample-rate 16000 \
+  /path/to/foo.wav \
+  /path/to/bar.wav
+
+(2) 1best
+./zipformer/pretrained_ctc.py \
+  --checkpoint ./zipformer/exp/pretrained.pt \
+  --HLG data/lang_bpe_500/HLG.pt \
+  --words-file data/lang_bpe_500/words.txt  \
+  --method 1best \
+  --sample-rate 16000 \
+  /path/to/foo.wav \
+  /path/to/bar.wav
+
+(3) nbest-rescoring
+./zipformer/pretrained_ctc.py \
+  --checkpoint ./zipformer/exp/pretrained.pt \
+  --HLG data/lang_bpe_500/HLG.pt \
+  --words-file data/lang_bpe_500/words.txt  \
+  --G data/lm/G_4_gram.pt \
+  --method nbest-rescoring \
+  --sample-rate 16000 \
+  /path/to/foo.wav \
+  /path/to/bar.wav
+
+
+(4) whole-lattice-rescoring
+./zipformer/pretrained_ctc.py \
+  --checkpoint ./zipformer/exp/pretrained.pt \
+  --HLG data/lang_bpe_500/HLG.pt \
+  --words-file data/lang_bpe_500/words.txt  \
+  --G data/lm/G_4_gram.pt \
+  --method whole-lattice-rescoring \
+  --sample-rate 16000 \
+  /path/to/foo.wav \
+  /path/to/bar.wav
+"""
+
+import argparse
+import logging
+import math
+from typing import List
+
+import k2
+import kaldifeat
+import sentencepiece as spm
+import torch
+import torchaudio
+from ctc_decode import get_decoding_params
+from torch.nn.utils.rnn import pad_sequence
+from train import add_model_arguments, get_params, get_model
+
+from icefall.decode import (
+    get_lattice,
+    one_best_decoding,
+    rescore_with_n_best_list,
+    rescore_with_whole_lattice,
+)
+from icefall.utils import get_texts
+
+
+def get_parser():
+    parser = argparse.ArgumentParser(
+        formatter_class=argparse.ArgumentDefaultsHelpFormatter
+    )
+
+    parser.add_argument(
+        "--checkpoint",
+        type=str,
+        required=True,
+        help="Path to the checkpoint. "
+        "The checkpoint is assumed to be saved by "
+        "icefall.checkpoint.save_checkpoint().",
+    )
+
+    parser.add_argument(
+        "--context-size",
+        type=int,
+        default=2,
+        help="The context size in the decoder. 1 means bigram; " "2 means tri-gram",
+    )
+
+    parser.add_argument(
+        "--words-file",
+        type=str,
+        help="""Path to words.txt.
+        Used only when method is not ctc-decoding.
+        """,
+    )
+
+    parser.add_argument(
+        "--HLG",
+        type=str,
+        help="""Path to HLG.pt.
+        Used only when method is not ctc-decoding.
+        """,
+    )
+
+    parser.add_argument(
+        "--bpe-model",
+        type=str,
+        help="""Path to bpe.model.
+        Used only when method is ctc-decoding.
+        """,
+    )
+
+    parser.add_argument(
+        "--method",
+        type=str,
+        default="1best",
+        help="""Decoding method.
+        Possible values are:
+        (0) ctc-decoding - Use CTC decoding. It uses a sentence
+            piece model, i.e., lang_dir/bpe.model, to convert
+            word pieces to words. It needs neither a lexicon
+            nor an n-gram LM.
+        (1) 1best - Use the best path as decoding output. Only
+            the transformer encoder output is used for decoding.
+            We call it HLG decoding.
+        (2) nbest-rescoring. Extract n paths from the decoding lattice,
+            rescore them with an LM, the path with
+            the highest score is the decoding result.
+            We call it HLG decoding + n-gram LM rescoring.
+        (3) whole-lattice-rescoring - Use an LM to rescore the
+            decoding lattice and then use 1best to decode the
+            rescored lattice.
+            We call it HLG decoding + n-gram LM rescoring.
+        """,
+    )
+
+    parser.add_argument(
+        "--G",
+        type=str,
+        help="""An LM for rescoring.
+        Used only when method is
+        whole-lattice-rescoring or nbest-rescoring.
+        It's usually a 4-gram LM.
+        """,
+    )
+
+    parser.add_argument(
+        "--num-paths",
+        type=int,
+        default=100,
+        help="""
+        Used only when method is attention-decoder.
+        It specifies the size of n-best list.""",
+    )
+
+    parser.add_argument(
+        "--ngram-lm-scale",
+        type=float,
+        default=1.3,
+        help="""
+        Used only when method is whole-lattice-rescoring and nbest-rescoring.
+        It specifies the scale for n-gram LM scores.
+        (Note: You need to tune it on a dataset.)
+        """,
+    )
+
+    parser.add_argument(
+        "--nbest-scale",
+        type=float,
+        default=1.0,
+        help="""
+        Used only when method is nbest-rescoring.
+        It specifies the scale for lattice.scores when
+        extracting n-best lists. A smaller value results in
+        more unique number of paths with the risk of missing
+        the best path.
+        """,
+    )
+
+    parser.add_argument(
+        "--num-classes",
+        type=int,
+        default=500,
+        help="""
+        Vocab size in the BPE model.
+        """,
+    )
+
+    parser.add_argument(
+        "--sample-rate",
+        type=int,
+        default=16000,
+        help="The sample rate of the input sound file",
+    )
+
+    parser.add_argument(
+        "sound_files",
+        type=str,
+        nargs="+",
+        help="The input sound file(s) to transcribe. "
+        "Supported formats are those supported by torchaudio.load(). "
+        "For example, wav and flac are supported. "
+        "The sample rate has to be 16kHz.",
+    )
+
+    add_model_arguments(parser)
+
+    return parser
+
+
+def read_sound_files(
+    filenames: List[str], expected_sample_rate: float = 16000
+) -> List[torch.Tensor]:
+    """Read a list of sound files into a list 1-D float32 torch tensors.
+    Args:
+      filenames:
+        A list of sound filenames.
+      expected_sample_rate:
+        The expected sample rate of the sound files.
+    Returns:
+      Return a list of 1-D float32 torch tensors.
+    """
+    ans = []
+    for f in filenames:
+        wave, sample_rate = torchaudio.load(f)
+        assert sample_rate == expected_sample_rate, (
+            f"expected sample rate: {expected_sample_rate}. " f"Given: {sample_rate}"
+        )
+        # We use only the first channel
+        ans.append(wave[0])
+    return ans
+
+
+@torch.no_grad()
+def main():
+    parser = get_parser()
+    args = parser.parse_args()
+
+    params = get_params()
+    # add decoding params
+    params.update(get_decoding_params())
+    params.update(vars(args))
+    params.vocab_size = params.num_classes
+    params.blank_id = 0
+
+    logging.info(f"{params}")
+
+    device = torch.device("cpu")
+    if torch.cuda.is_available():
+        device = torch.device("cuda", 0)
+
+    logging.info(f"device: {device}")
+
+    logging.info("Creating model")
+    model = get_model(params)
+
+    num_param = sum([p.numel() for p in model.parameters()])
+    logging.info(f"Number of model parameters: {num_param}")
+
+    checkpoint = torch.load(args.checkpoint, map_location="cpu")
+    model.load_state_dict(checkpoint["model"], strict=False)
+    model.to(device)
+    model.eval()
+
+    logging.info("Constructing Fbank computer")
+    opts = kaldifeat.FbankOptions()
+    opts.device = device
+    opts.frame_opts.dither = 0
+    opts.frame_opts.snip_edges = False
+    opts.frame_opts.samp_freq = params.sample_rate
+    opts.mel_opts.num_bins = params.feature_dim
+
+    fbank = kaldifeat.Fbank(opts)
+
+    logging.info(f"Reading sound files: {params.sound_files}")
+    waves = read_sound_files(
+        filenames=params.sound_files, expected_sample_rate=params.sample_rate
+    )
+    waves = [w.to(device) for w in waves]
+
+    logging.info("Decoding started")
+    features = fbank(waves)
+    feature_lengths = [f.size(0) for f in features]
+
+    features = pad_sequence(features, batch_first=True, padding_value=math.log(1e-10))
+    feature_lengths = torch.tensor(feature_lengths, device=device)
+
+    encoder_out, encoder_out_lens = model.forward_encoder(features, feature_lengths)
+    ctc_output = model.ctc_output(encoder_out)  # (N, T, C)
+
+    batch_size = ctc_output.shape[0]
+    supervision_segments = torch.tensor(
+        [
+            [i, 0, feature_lengths[i].item() // params.subsampling_factor]
+            for i in range(batch_size)
+        ],
+        dtype=torch.int32,
+    )
+
+    if params.method == "ctc-decoding":
+        logging.info("Use CTC decoding")
+        bpe_model = spm.SentencePieceProcessor()
+        bpe_model.load(params.bpe_model)
+        max_token_id = params.num_classes - 1
+
+        H = k2.ctc_topo(
+            max_token=max_token_id,
+            modified=False,
+            device=device,
+        )
+
+        lattice = get_lattice(
+            nnet_output=ctc_output,
+            decoding_graph=H,
+            supervision_segments=supervision_segments,
+            search_beam=params.search_beam,
+            output_beam=params.output_beam,
+            min_active_states=params.min_active_states,
+            max_active_states=params.max_active_states,
+            subsampling_factor=params.subsampling_factor,
+        )
+
+        best_path = one_best_decoding(
+            lattice=lattice, use_double_scores=params.use_double_scores
+        )
+        token_ids = get_texts(best_path)
+        hyps = bpe_model.decode(token_ids)
+        hyps = [s.split() for s in hyps]
+    elif params.method in [
+        "1best",
+        "nbest-rescoring",
+        "whole-lattice-rescoring",
+    ]:
+        logging.info(f"Loading HLG from {params.HLG}")
+        HLG = k2.Fsa.from_dict(torch.load(params.HLG, map_location="cpu"))
+        HLG = HLG.to(device)
+        if not hasattr(HLG, "lm_scores"):
+            # For whole-lattice-rescoring and attention-decoder
+            HLG.lm_scores = HLG.scores.clone()
+
+        if params.method in [
+            "nbest-rescoring",
+            "whole-lattice-rescoring",
+        ]:
+            logging.info(f"Loading G from {params.G}")
+            G = k2.Fsa.from_dict(torch.load(params.G, map_location="cpu"))
+            G = G.to(device)
+            if params.method == "whole-lattice-rescoring":
+                # Add epsilon self-loops to G as we will compose
+                # it with the whole lattice later
+                G = k2.add_epsilon_self_loops(G)
+                G = k2.arc_sort(G)
+
+            # G.lm_scores is used to replace HLG.lm_scores during
+            # LM rescoring.
+            G.lm_scores = G.scores.clone()
+
+        lattice = get_lattice(
+            nnet_output=ctc_output,
+            decoding_graph=HLG,
+            supervision_segments=supervision_segments,
+            search_beam=params.search_beam,
+            output_beam=params.output_beam,
+            min_active_states=params.min_active_states,
+            max_active_states=params.max_active_states,
+            subsampling_factor=params.subsampling_factor,
+        )
+
+        if params.method == "1best":
+            logging.info("Use HLG decoding")
+            best_path = one_best_decoding(
+                lattice=lattice, use_double_scores=params.use_double_scores
+            )
+        if params.method == "nbest-rescoring":
+            logging.info("Use HLG decoding + LM rescoring")
+            best_path_dict = rescore_with_n_best_list(
+                lattice=lattice,
+                G=G,
+                num_paths=params.num_paths,
+                lm_scale_list=[params.ngram_lm_scale],
+                nbest_scale=params.nbest_scale,
+            )
+            best_path = next(iter(best_path_dict.values()))
+        elif params.method == "whole-lattice-rescoring":
+            logging.info("Use HLG decoding + LM rescoring")
+            best_path_dict = rescore_with_whole_lattice(
+                lattice=lattice,
+                G_with_epsilon_loops=G,
+                lm_scale_list=[params.ngram_lm_scale],
+            )
+            best_path = next(iter(best_path_dict.values()))
+
+        hyps = get_texts(best_path)
+        word_sym_table = k2.SymbolTable.from_file(params.words_file)
+        hyps = [[word_sym_table[i] for i in ids] for ids in hyps]
+    else:
+        raise ValueError(f"Unsupported decoding method: {params.method}")
+
+    s = "\n"
+    for filename, hyp in zip(params.sound_files, hyps):
+        words = " ".join(hyp)
+        s += f"{filename}:\n{words}\n\n"
+    logging.info(s)
+
+    logging.info("Decoding Done")
+
+
+if __name__ == "__main__":
+    formatter = "%(asctime)s %(levelname)s [%(filename)s:%(lineno)d] %(message)s"
+
+    logging.basicConfig(format=formatter, level=logging.INFO)
+    main()
diff --git a/egs/librispeech/ASR/zipformer/train.py b/egs/librispeech/ASR/zipformer/train.py
index 481ea9d13..8553581d5 100755
--- a/egs/librispeech/ASR/zipformer/train.py
+++ b/egs/librispeech/ASR/zipformer/train.py
@@ -44,6 +44,10 @@ export CUDA_VISIBLE_DEVICES="0,1,2,3"
   --full-libri 1 \
   --max-duration 1000
 
+It supports training with:
+  - transducer loss (default), with `--use-transducer True --use-ctc False`
+  - ctc loss (not recommended), with `--use-transducer False --use-ctc True`
+  - transducer loss & ctc loss, with `--use-transducer True --use-ctc True`
 """