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#10406 new defect

Change in audio track 'initial_padding' behaviour from ffmpeg v5 to ffmpeg v6

Reported by:	Garry Robertson	Owned by:
Priority:	normal	Component:	undetermined
Version:	6.0	Keywords:
Cc:		Blocked By:
Blocking:		Reproduced by developer:	no
Analyzed by developer:	no

Description

Summary of the bug:
When converting EAC3 audio tracks to AC3 in Matroska containers, ffmpeg v6 is setting a non-zero value on the 'initial_padding', 'start_pts', and 'start_time' values for the audio track. This is a change in behaviour from ffmpeg v5.

While the converted file is playing correctly in modern players, it is causing the audio codec not to be recognised in an older player (Sony TV).

This change to 'initial_padding', etc does not happen if encoding into an mp4 container. The value remains as 0, consistant with ffmpeg v5.

Initial probe of eac3 file:

% ffprobe -show_streams "AC3 v6.mkv"
ffprobe version 6.0-full_build-www.gyan.dev Copyright (c) 2007-2023 the FFmpeg developers
  built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libvpl --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil      58.  2.100 / 58.  2.100
  libavcodec     60.  3.100 / 60.  3.100
  libavformat    60.  3.100 / 60.  3.100
  libavdevice    60.  1.100 / 60.  1.100
  libavfilter     9.  3.100 /  9.  3.100
  libswscale      7.  1.100 /  7.  1.100
  libswresample   4. 10.100 /  4. 10.100
  libpostproc    57.  1.100 / 57.  1.100
Input #0, matroska,webm, from '\\THISTLEDOWN\Media Server 3\Miscellaneous\Convertor Test\EAC3.mkv':
  Metadata:
    encoder         : libebml v1.4.4 + libmatroska v1.7.1
    creation_time   : 2023-06-08T03:57:29.000000Z
  Duration: 00:00:05.05, start: 0.000000, bitrate: 847 kb/s
  Stream #0:0(eng): Video: h264 (High), yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn (default)
  Stream #0:1: Audio: eac3, 48000 Hz, 5.1(side), fltp, 768 kb/s (default)
[STREAM]
index=0
codec_name=h264
codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
profile=High
codec_type=video
codec_tag_string=[0][0][0][0]
codec_tag=0x0000
width=1280
height=720
coded_width=1280
coded_height=720
closed_captions=0
film_grain=0
has_b_frames=1
sample_aspect_ratio=1:1
display_aspect_ratio=16:9
pix_fmt=yuv420p
level=31
color_range=tv
color_space=bt709
color_transfer=bt709
color_primaries=bt709
chroma_location=topleft
field_order=progressive
refs=1
is_avc=true
nal_length_size=4
id=N/A
r_frame_rate=24000/1001
avg_frame_rate=24000/1001
time_base=1/1000
start_pts=0
start_time=0.000000
duration_ts=N/A
duration=N/A
bit_rate=N/A
max_bit_rate=N/A
bits_per_raw_sample=8
nb_frames=N/A
nb_read_frames=N/A
nb_read_packets=N/A
extradata_size=50
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
DISPOSITION:timed_thumbnails=0
DISPOSITION:captions=0
DISPOSITION:descriptions=0
DISPOSITION:metadata=0
DISPOSITION:dependent=0
DISPOSITION:still_image=0
TAG:language=eng
[/STREAM]
[STREAM]
index=1
codec_name=eac3
codec_long_name=ATSC A/52B (AC-3, E-AC-3)
profile=unknown
codec_type=audio
codec_tag_string=[0][0][0][0]
codec_tag=0x0000
sample_fmt=fltp
sample_rate=48000
channels=6
channel_layout=5.1(side)
bits_per_sample=0
initial_padding=0  <------
id=N/A
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/1000
start_pts=0  <------
start_time=0.000000  <------
duration_ts=N/A
duration=N/A
bit_rate=768000
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=N/A
nb_read_frames=N/A
nb_read_packets=N/A
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
DISPOSITION:timed_thumbnails=0
DISPOSITION:captions=0
DISPOSITION:descriptions=0
DISPOSITION:metadata=0
DISPOSITION:dependent=0
DISPOSITION:still_image=0
[/STREAM]

NOTE: Audio initial_padding=0, etc.

How to reproduce with ffmpeg v6:

% ffmpeg -y -i EAC3.mkv -c:v copy -c:a ac3 "AC3 v6.mkv"
ffmpeg version 6.0-full_build-www.gyan.dev Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libvpl --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil      58.  2.100 / 58.  2.100
  libavcodec     60.  3.100 / 60.  3.100
  libavformat    60.  3.100 / 60.  3.100
  libavdevice    60.  1.100 / 60.  1.100
  libavfilter     9.  3.100 /  9.  3.100
  libswscale      7.  1.100 /  7.  1.100
  libswresample   4. 10.100 /  4. 10.100
  libpostproc    57.  1.100 / 57.  1.100
Input #0, matroska,webm, from '\\THISTLEDOWN\Media Server 3\Miscellaneous\Convertor Test\EAC3.mkv':
  Metadata:
    encoder         : libebml v1.4.4 + libmatroska v1.7.1
    creation_time   : 2023-06-08T03:57:29.000000Z
  Duration: 00:00:05.05, start: 0.000000, bitrate: 847 kb/s
  Stream #0:0(eng): Video: h264 (High), yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn (default)
  Stream #0:1: Audio: eac3, 48000 Hz, 5.1(side), fltp, 768 kb/s (default)
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (eac3 (native) -> ac3 (native))
Press [q] to stop, [?] for help
Output #0, matroska, to '\\THISTLEDOWN\Media Server 3\Miscellaneous\Convertor Test\AC3 v6.mkv':
  Metadata:
    encoder         : Lavf60.3.100
  Stream #0:0(eng): Video: h264 (High) (H264 / 0x34363248), yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 23.98 fps, 23.98 tbr, 1k tbn (default)
  Stream #0:1: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, 5.1(side), fltp, 448 kb/s (default)
    Metadata:
      encoder         : Lavc60.3.100 ac3
frame=  121 fps=0.0 q=-1.0 Lsize=     322kB time=00:00:04.98 bitrate= 529.3kbits/s speed= 114x
video:45kB audio:275kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.816106%

Probe of new ac3 file:

% ffprobe -show_streams "AC3 v6.mkv"
ffprobe version 6.0-full_build-www.gyan.dev Copyright (c) 2007-2023 the FFmpeg developers
  built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libvpl --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil      58.  2.100 / 58.  2.100
  libavcodec     60.  3.100 / 60.  3.100
  libavformat    60.  3.100 / 60.  3.100
  libavdevice    60.  1.100 / 60.  1.100
  libavfilter     9.  3.100 /  9.  3.100
  libswscale      7.  1.100 /  7.  1.100
  libswresample   4. 10.100 /  4. 10.100
  libpostproc    57.  1.100 / 57.  1.100
Input #0, matroska,webm, from '\\THISTLEDOWN\Media Server 3\Miscellaneous\Convertor Test\AC3 v6.mkv':
  Metadata:
    ENCODER         : Lavf60.3.100
  Duration: 00:00:05.05, start: -0.005000, bitrate: 523 kb/s
  Stream #0:0(eng): Video: h264 (High), yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn (default)
    Metadata:
      DURATION        : 00:00:05.046000000
  Stream #0:1: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s (default)
    Metadata:
      ENCODER         : Lavc60.3.100 ac3
      DURATION        : 00:00:05.024000000
[STREAM]
index=0
codec_name=h264
codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
profile=High
codec_type=video
codec_tag_string=[0][0][0][0]
codec_tag=0x0000
width=1280
height=720
coded_width=1280
coded_height=720
closed_captions=0
film_grain=0
has_b_frames=1
sample_aspect_ratio=1:1
display_aspect_ratio=16:9
pix_fmt=yuv420p
level=31
color_range=tv
color_space=bt709
color_transfer=bt709
color_primaries=bt709
chroma_location=topleft
field_order=progressive
refs=1
is_avc=true
nal_length_size=4
id=N/A
r_frame_rate=24000/1001
avg_frame_rate=24000/1001
time_base=1/1000
start_pts=0
start_time=0.000000
duration_ts=N/A
duration=N/A
bit_rate=N/A
max_bit_rate=N/A
bits_per_raw_sample=8
nb_frames=N/A
nb_read_frames=N/A
nb_read_packets=N/A
extradata_size=50
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
DISPOSITION:timed_thumbnails=0
DISPOSITION:captions=0
DISPOSITION:descriptions=0
DISPOSITION:metadata=0
DISPOSITION:dependent=0
DISPOSITION:still_image=0
TAG:language=eng
TAG:DURATION=00:00:05.046000000
[/STREAM]
[STREAM]
index=1
codec_name=ac3
codec_long_name=ATSC A/52A (AC-3)
profile=unknown
codec_type=audio
codec_tag_string=[0][0][0][0]
codec_tag=0x0000
sample_fmt=fltp
sample_rate=48000
channels=6
channel_layout=5.1(side)
bits_per_sample=0
initial_padding=256  <------
id=N/A
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/1000
start_pts=-5  <------
start_time=-0.005000  <------
duration_ts=N/A
duration=N/A
bit_rate=448000
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=N/A
nb_read_frames=N/A
nb_read_packets=N/A
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
DISPOSITION:timed_thumbnails=0
DISPOSITION:captions=0
DISPOSITION:descriptions=0
DISPOSITION:metadata=0
DISPOSITION:dependent=0
DISPOSITION:still_image=0
TAG:ENCODER=Lavc60.3.100 ac3
TAG:DURATION=00:00:05.024000000
[/STREAM]

NOTE: Audio initial_padding=256, etc.

How to reproduce with ffmpeg v5:

% ffmpeg -y -i EAC3.mkv -c:v copy -c:a ac3 "AC3 v5.mkv"
ffmpeg version 5.1.2-essentials_build-www.gyan.dev Copyright (c) 2000-2022 the FFmpeg developers
  built with gcc 12.1.0 (Rev2, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-sdl2 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libgme --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libtheora --enable-libvo-amrwbenc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-librubberband
  libavutil      57. 28.100 / 57. 28.100
  libavcodec     59. 37.100 / 59. 37.100
  libavformat    59. 27.100 / 59. 27.100
  libavdevice    59.  7.100 / 59.  7.100
  libavfilter     8. 44.100 /  8. 44.100
  libswscale      6.  7.100 /  6.  7.100
  libswresample   4.  7.100 /  4.  7.100
  libpostproc    56.  6.100 / 56.  6.100
Input #0, matroska,webm, from '\\THISTLEDOWN\Media Server 3\Miscellaneous\Convertor Test\EAC3.mkv':
  Metadata:
    encoder         : libebml v1.4.4 + libmatroska v1.7.1
    creation_time   : 2023-06-08T03:57:29.000000Z
  Duration: 00:00:05.05, start: 0.000000, bitrate: 847 kb/s
  Stream #0:0(eng): Video: h264 (High), yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn (default)
  Stream #0:1: Audio: eac3, 48000 Hz, 5.1(side), fltp, 768 kb/s (default)
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (eac3 (native) -> ac3 (native))
Press [q] to stop, [?] for help
Output #0, matroska, to '\\THISTLEDOWN\Media Server 3\Miscellaneous\Convertor Test\AC3 v5.mkv':
  Metadata:
    encoder         : Lavf59.27.100
  Stream #0:0(eng): Video: h264 (High) (H264 / 0x34363248), yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 23.98 fps, 23.98 tbr, 1k tbn (default)
  Stream #0:1: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, 5.1(side), fltp, 448 kb/s (default)
    Metadata:
      encoder         : Lavc59.37.100 ac3
frame=  121 fps=0.0 q=-1.0 Lsize=     322kB time=00:00:05.01 bitrate= 525.9kbits/s speed= 176x
video:45kB audio:275kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.815495%

v5 Probe of new ac3 (v5) file:

% ffprobe -show_streams "AC3 v5.mkv"
ffprobe version 5.1.2-essentials_build-www.gyan.dev Copyright (c) 2007-2022 the FFmpeg developers
  built with gcc 12.1.0 (Rev2, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-sdl2 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libgme --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libtheora --enable-libvo-amrwbenc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-librubberband
  libavutil      57. 28.100 / 57. 28.100
  libavcodec     59. 37.100 / 59. 37.100
  libavformat    59. 27.100 / 59. 27.100
  libavdevice    59.  7.100 / 59.  7.100
  libavfilter     8. 44.100 /  8. 44.100
  libswscale      6.  7.100 /  6.  7.100
  libswresample   4.  7.100 /  4.  7.100
  libpostproc    56.  6.100 / 56.  6.100
Input #0, matroska,webm, from '\\THISTLEDOWN\Media Server 3\Miscellaneous\Convertor Test\AC3 v5.mkv':
  Metadata:
    ENCODER         : Lavf59.27.100
  Duration: 00:00:05.05, start: 0.000000, bitrate: 522 kb/s
  Stream #0:0(eng): Video: h264 (High), yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn (default)
    Metadata:
      DURATION        : 00:00:05.051000000
  Stream #0:1: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s (default)
    Metadata:
      ENCODER         : Lavc59.37.100 ac3
      DURATION        : 00:00:05.024000000
[STREAM]
index=0
codec_name=h264
codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
profile=High
codec_type=video
codec_tag_string=[0][0][0][0]
codec_tag=0x0000
width=1280
height=720
coded_width=1280
coded_height=720
closed_captions=0
film_grain=0
has_b_frames=1
sample_aspect_ratio=1:1
display_aspect_ratio=16:9
pix_fmt=yuv420p
level=31
color_range=tv
color_space=bt709
color_transfer=bt709
color_primaries=bt709
chroma_location=topleft
field_order=progressive
refs=1
is_avc=true
nal_length_size=4
id=N/A
r_frame_rate=24000/1001
avg_frame_rate=24000/1001
time_base=1/1000
start_pts=5
start_time=0.005000
duration_ts=N/A
duration=N/A
bit_rate=N/A
max_bit_rate=N/A
bits_per_raw_sample=8
nb_frames=N/A
nb_read_frames=N/A
nb_read_packets=N/A
extradata_size=50
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
DISPOSITION:timed_thumbnails=0
DISPOSITION:captions=0
DISPOSITION:descriptions=0
DISPOSITION:metadata=0
DISPOSITION:dependent=0
DISPOSITION:still_image=0
TAG:language=eng
TAG:DURATION=00:00:05.051000000
[/STREAM]
[STREAM]
index=1
codec_name=ac3
codec_long_name=ATSC A/52A (AC-3)
profile=unknown
codec_type=audio
codec_tag_string=[0][0][0][0]
codec_tag=0x0000
sample_fmt=fltp
sample_rate=48000
channels=6
channel_layout=5.1(side)
bits_per_sample=0
id=N/A
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/1000
start_pts=0  <------
start_time=0.000000  <------
duration_ts=N/A
duration=N/A
bit_rate=448000
max_bit_rate=N/A
bits_per_raw_sample=N/A
nb_frames=N/A
nb_read_frames=N/A
nb_read_packets=N/A
DISPOSITION:default=1
DISPOSITION:dub=0
DISPOSITION:original=0
DISPOSITION:comment=0
DISPOSITION:lyrics=0
DISPOSITION:karaoke=0
DISPOSITION:forced=0
DISPOSITION:hearing_impaired=0
DISPOSITION:visual_impaired=0
DISPOSITION:clean_effects=0
DISPOSITION:attached_pic=0
DISPOSITION:timed_thumbnails=0
DISPOSITION:captions=0
DISPOSITION:descriptions=0
DISPOSITION:metadata=0
DISPOSITION:dependent=0
DISPOSITION:still_image=0
TAG:ENCODER=Lavc59.37.100 ac3
TAG:DURATION=00:00:05.024000000
[/STREAM]

A probe of this v5 file shows audio 'start_pts=0', etc. Interestingly, 'initial_padding' is not reported, although it shows up as zero if v6 version of ffprobe is used

It's not clear to me whether this is a bug, or a deliberate change in behaviour. However, its impact is preventing me adopting use of ffmpeg v6.

Attachments (4)

EAC3.mkv (522.4 KB ) - added by Garry Robertson 11 months ago.: Sample eac3 file
AC3 v6.mkv (322.2 KB ) - added by Garry Robertson 11 months ago.: AC3 file converted with ffmpeg v6
AC3 v5.mkv (322.2 KB ) - added by Garry Robertson 11 months ago.: AC3 file converted with ffmpeg v5
AC3 v6.mp4 (324.7 KB ) - added by Garry Robertson 11 months ago.: AC3 mp4 file converted with ffmpeg v6

Download all attachments as: .zip

Change History (7)

by Garry Robertson, 11 months ago

Attachment:	EAC3.mkv added

Sample eac3 file

by Garry Robertson, 11 months ago

Attachment:	AC3 v6.mkv added

AC3 file converted with ffmpeg v6

by Garry Robertson, 11 months ago

Attachment:	AC3 v5.mkv added

AC3 file converted with ffmpeg v5

follow-up: 2 comment:1 by Balling, 11 months ago

The value remains as 0, consistant with ffmpeg v5.

No, in fact the editlist correctly writes the priming of 256 samples.

in reply to: 1 comment:2 by Garry Robertson, 11 months ago

Replying to Balling:

The value remains as 0, consistant with ffmpeg v5.

No, in fact the editlist correctly writes the priming of 256 samples.

Thanks for the reply. My observation for an mp4 conversion (ffmpeg v6) is this:

  ffmpeg -y -i EAC3.mkv -c:v copy -c:a ac3 "AC3 v6.mp4"

  ffprobe -show_streams "AC3 v6.mp4"

shows: initial_padding=0 on the audio stream.

... and it plays correctly in the older player I referred to. I have attached the mp4 file.

by Garry Robertson, 11 months ago

Attachment:	AC3 v6.mp4 added

AC3 mp4 file converted with ffmpeg v6

comment:3 by Garry Robertson, 11 months ago

Another observation:

Extracting an ac3 audio file then re-merging it back into the original mkv container produces a file with initial_padding=0 on the audio stream.

  ffmpeg -y -i EAC3.mkv -c:v copy -c:a ac3 "AC3 v6.ac3"

then merge back into EAC3.mkv with mkvmerge tool.

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