Begin to support CTC models (#119)

Please see https://k2-fsa.github.io/sherpa/onnx/pretrained_models/offline-ctc/nemo/index.html for a list of pre-trained CTC models from NeMo.

python-api-examples/offline-decode-files.py

@@ -6,7 +6,7 @@
 This file demonstrates how to use sherpa-onnx Python API to transcribe
 file(s) with a non-streaming model.
 
-paraformer Usage:
+(1) For paraformer
     ./python-api-examples/offline-decode-files.py  \
       --tokens=/path/to/tokens.txt \
       --paraformer=/path/to/paraformer.onnx \
@@ -18,7 +18,7 @@ paraformer Usage:
       /path/to/0.wav \
       /path/to/1.wav
 
-transducer Usage:
+(2) For transducer models from icefall
     ./python-api-examples/offline-decode-files.py  \
       --tokens=/path/to/tokens.txt \
       --encoder=/path/to/encoder.onnx \
@@ -32,6 +32,8 @@ transducer Usage:
       /path/to/0.wav \
       /path/to/1.wav
 
+(3) For CTC models from NeMo
+
 Please refer to
 https://k2-fsa.github.io/sherpa/onnx/index.html
 to install sherpa-onnx and to download the pre-trained models
@@ -83,7 +85,14 @@ def get_args():
         "--paraformer",
         default="",
         type=str,
-        help="Path to the paraformer model",
+        help="Path to the model.onnx from Paraformer",
+    )
+
+    parser.add_argument(
+        "--nemo-ctc",
+        default="",
+        type=str,
+        help="Path to the model.onnx from NeMo CTC",
     )
 
     parser.add_argument(
@@ -171,11 +180,14 @@ def main():
     args = get_args()
     assert_file_exists(args.tokens)
     assert args.num_threads > 0, args.num_threads
-    if len(args.encoder) > 0:
+    if args.encoder:
+        assert len(args.paraformer) == 0, args.paraformer
+        assert len(args.nemo_ctc) == 0, args.nemo_ctc
+
         assert_file_exists(args.encoder)
         assert_file_exists(args.decoder)
         assert_file_exists(args.joiner)
-        assert len(args.paraformer) == 0, args.paraformer
+
         recognizer = sherpa_onnx.OfflineRecognizer.from_transducer(
             encoder=args.encoder,
             decoder=args.decoder,
@@ -187,8 +199,10 @@ def main():
             decoding_method=args.decoding_method,
             debug=args.debug,
         )
-    else:
+    elif args.paraformer:
+        assert len(args.nemo_ctc) == 0, args.nemo_ctc
         assert_file_exists(args.paraformer)
+
         recognizer = sherpa_onnx.OfflineRecognizer.from_paraformer(
             paraformer=args.paraformer,
             tokens=args.tokens,
@@ -198,6 +212,19 @@ def main():
             decoding_method=args.decoding_method,
             debug=args.debug,
         )
+    elif args.nemo_ctc:
+        recognizer = sherpa_onnx.OfflineRecognizer.from_nemo_ctc(
+            model=args.nemo_ctc,
+            tokens=args.tokens,
+            num_threads=args.num_threads,
+            sample_rate=args.sample_rate,
+            feature_dim=args.feature_dim,
+            decoding_method=args.decoding_method,
+            debug=args.debug,
+        )
+    else:
+        print("Please specify at least one model")
+        return
 
     print("Started!")
     start_time = time.time()
@@ -225,12 +252,14 @@ def main():
         print("-" * 10)
 
     elapsed_seconds = end_time - start_time
-    rtf = elapsed_seconds / duration
+    rtf = elapsed_seconds / total_duration
     print(f"num_threads: {args.num_threads}")
     print(f"decoding_method: {args.decoding_method}")
-    print(f"Wave duration: {duration:.3f} s")
+    print(f"Wave duration: {total_duration:.3f} s")
     print(f"Elapsed time: {elapsed_seconds:.3f} s")
-    print(f"Real time factor (RTF): {elapsed_seconds:.3f}/{duration:.3f} = {rtf:.3f}")
+    print(
+        f"Real time factor (RTF): {elapsed_seconds:.3f}/{total_duration:.3f} = {rtf:.3f}"
+    )
 
 
 if __name__ == "__main__":

python-api-examples/online-decode-files.py

@@ -172,12 +172,14 @@ def main():
         print("-" * 10)
 
     elapsed_seconds = end_time - start_time
-    rtf = elapsed_seconds / duration
+    rtf = elapsed_seconds / total_duration
     print(f"num_threads: {args.num_threads}")
     print(f"decoding_method: {args.decoding_method}")
-    print(f"Wave duration: {duration:.3f} s")
+    print(f"Wave duration: {total_duration:.3f} s")
     print(f"Elapsed time: {elapsed_seconds:.3f} s")
-    print(f"Real time factor (RTF): {elapsed_seconds:.3f}/{duration:.3f} = {rtf:.3f}")
+    print(
+        f"Real time factor (RTF): {elapsed_seconds:.3f}/{total_duration:.3f} = {rtf:.3f}"
+    )
 
 
 if __name__ == "__main__":