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fix: Fix pyav cannot access time_base as a decoder when converting dataset from v2.1 to v3 #2115

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fix: Fix pyav cannot access time_base as a decoder when converting dataset from v2.1 to v3 #2115

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84facd6
Fix pyav Cannot access time_base as a decoder
jackvial Oct 4, 2025
1db8ee0
Merge branch 'main' into jv/fix-pyav-error
michel-aractingi Oct 7, 2025
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20 changes: 11 additions & 9 deletions src/lerobot/datasets/video_utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -447,15 +447,17 @@ def concatenate_video_files(
# Replicate input streams in output container
stream_map = {}
for input_stream in input_container.streams:
if input_stream.type in ("video", "audio", "subtitle"): # only copy compatible streams
stream_map[input_stream.index] = output_container.add_stream_from_template(
template=input_stream, opaque=True
)
stream_map[
input_stream.index
].time_base = (
input_stream.time_base
) # set the time base to the input stream time base (missing in the codec context)
if input_stream.type in ("video", "audio", "subtitle"): # only copy compatible
output_stream = output_container.add_stream_from_template(template=input_stream, opaque=True)

codec_context = output_stream.codec_context

# Prevent "RuntimeError: Cannot access 'time_base' as a decoder" error
# Only try to mutate codec_context.time_base if is_encoder=True
if codec_context is not None and getattr(codec_context, "is_encoder", False):
codec_context.time_base = input_stream.time_base

stream_map[input_stream.index] = output_stream

# Demux + remux packets (no re-encode)
for packet in input_container.demux():
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