[FFmpeg-trac] #6841(avformat:open): 1ms gap in WebM Opus files encoded with ffmpeg
FFmpeg
trac at avcodec.org
Fri Dec 1 02:32:51 EET 2017
#6841: 1ms gap in WebM Opus files encoded with ffmpeg
------------------------------------+------------------------------------
Reporter: ntrrgc | Owner:
Type: defect | Status: open
Priority: normal | Component: avformat
Version: git-master | Resolution:
Keywords: mkv opus | Blocked By:
Blocking: | Reproduced by developer: 1
Analyzed by developer: 0 |
------------------------------------+------------------------------------
Comment (by mkver):
This seems to be a problem with encoder delay (that opus signals
explicitly) and rounding timestamps too early. In more detail: The
reference opus encoder has a default encoding delay of 312 samples (6.5ms
at a sample rate of 48000.) So the first audio block has a PTS of -6.5ms;
the second of 13.5ms. Upon conversion to ms precision (the Matroska muxer
uses 1/1000 as timebase) the first becomes -7ms, the second 14ms. This is
then shifted by default to avoid negative timestamps (depends upon
-avoid_negative_ts). Here is the log:
{{{
ffmpeg started on 2017-12-01 at 00:48:14
Report written to "ffmpeg-20171201-004814.log"
Command line:
ffmpeg -debug_ts -report -i sin.opus -c copy sin.mka
ffmpeg version N-89341-gd13b8f68d7 Copyright (c) 2000-2017 the FFmpeg
developers
built with gcc 7.2.0 (Rev1, Built by MSYS2 project)
configuration: --disable-static --enable-shared --enable-avisynth
--enable-gcrypt --enable-libopus --enable-libvorbis --enable-gnutls
--enable-libbluray --enable-libmfx --enable-libwavpack --enable-gpl
--disable-decoder=h264_cuvid --disable-decoder=hevc_cuvid --disable-
decoder=mjpeg_cuvid --disable-decoder=mpeg1_cuvid --disable-
decoder=mpeg2_cuvid --disable-decoder=mpeg4_cuvid --disable-
decoder=vc1_cuvid --disable-decoder=vp8_cuvid --disable-decoder=vp9_cuvid
--disable-encoder=dca --disable-encoder=nellymoser --disable-
encoder=real_144 --disable-encoder=truehd --disable-encoder=vorbis
--disable-encoder=sonic --disable-encoder=sonicls --disable-encoder=amv
--disable-encoder=asv1 --disable-encoder=asv2 --disable-encoder=flashsv
--disable-encoder=flashsv2 --disable-encoder=roqvideo --disable-
encoder=svq1 --disable-encoder=zmbv --disable-encoder=zlib --disable-
encoder=snow --disable-encoder=cinepak --disable-encoder=h264_nvenc
--disable-encoder=hevc_nvenc --disable-encoder=nvenc_hevc --disable-
encoder=nvenc -- libavutil 56. 4.100 / 56. 4.100
libavcodec 58. 6.102 / 58. 6.102
libavformat 58. 2.103 / 58. 2.103
libavdevice 58. 0.100 / 58. 0.100
libavfilter 7. 5.100 / 7. 5.100
libswscale 5. 0.101 / 5. 0.101
libswresample 3. 0.101 / 3. 0.101
libpostproc 55. 0.100 / 55. 0.100
Splitting the commandline.
Reading option '-debug_ts' ... matched as option 'debug_ts' (print
timestamp debugging info) with argument '1'.
Reading option '-report' ... matched as option 'report' (generate a
report) with argument '1'.
Reading option '-i' ... matched as input url with argument 'sin.opus'.
Reading option '-c' ... matched as option 'c' (codec name) with argument
'copy'.
Reading option 'sin.mka' ... matched as output url.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option debug_ts (print timestamp debugging info) with argument 1.
Applying option report (generate a report) with argument 1.
Successfully parsed a group of options.
Parsing a group of options: input url sin.opus.
Successfully parsed a group of options.
Opening an input file: sin.opus.
[NULL @ 00000000005f5a40] Opening 'sin.opus' for reading
[file @ 00000000005dea00] Setting default whitelist 'file,crypto'
[ogg @ 00000000005f5a40] Format ogg probed with size=2048 and score=100
[ogg @ 00000000005f5a40] 684 bytes of comment header remain
[ogg @ 00000000005f5a40] Before avformat_find_stream_info() pos: 2007
bytes read:2007 seeks:0 nb_streams:1
[ogg @ 00000000005f5a40] All info found
[ogg @ 00000000005f5a40] After avformat_find_stream_info() pos: 2007 bytes
read:2007 seeks:0 frames:1
Input #0, ogg, from 'sin.opus':
Duration: 00:00:00.10, start: 0.000000, bitrate: 160 kb/s
Stream #0:0, 1, 1/48000: Audio: opus, 48000 Hz, mono, fltp
Metadata:
ENCODER : opusenc from opus-tools 0.1.10-9-gbd65450
Successfully opened the file.
Parsing a group of options: output url sin.mka.
Applying option c (codec name) with argument copy.
Successfully parsed a group of options.
Opening an output file: sin.mka.
[file @ 00000000005debe0] Setting default whitelist 'file,crypto'
Successfully opened the file.
Output #0, matroska, to 'sin.mka':
Metadata:
encoder : Lavf58.2.103
Stream #0:0, 0, 1/1000: Audio: opus ([255][255][255][255] /
0xFFFFFFFF), 48000 Hz, mono, fltp
Metadata:
ENCODER : opusenc from opus-tools 0.1.10-9-gbd65450
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
cur_dts is invalid (this is harmless if it occurs once at the start per
stream)
demuxer -> ist_index:0 type:audio next_dts:NOPTS next_dts_time:NOPTS
next_pts:NOPTS next_pts_time:NOPTS pkt_pts:-312 pkt_pts_time:-0.0065
pkt_dts:-312 pkt_dts_time:-0.0065 off:0 off_time:0
demuxer+ffmpeg -> ist_index:0 type:audio pkt_pts:-312 pkt_pts_time:-0.0065
pkt_dts:-312 pkt_dts_time:-0.0065 off:0 off_time:0
muxer <- type:audio pkt_pts:-7 pkt_pts_time:-0.007 pkt_dts:-7
pkt_dts_time:-0.007 size:300
[matroska @ 00000000005f76c0] get_metadata_duration returned: 0
demuxer -> ist_index:0 type:audio next_dts:-6500 next_dts_time:-0.0065
next_pts:-6500 next_pts_time:-0.0065 pkt_pts:648 pkt_pts_time:0.0135
pkt_dts:648 pkt_dts_time:0.0135 off:0 off_time:0
demuxer+ffmpeg -> ist_index:0 type:audio pkt_pts:648 pkt_pts_time:0.0135
pkt_dts:648 pkt_dts_time:0.0135 off:0 off_time:0
muxer <- type:audio pkt_pts:14 pkt_pts_time:0.014 pkt_dts:14
pkt_dts_time:0.014 size:165
[matroska @ 00000000005f76c0] Writing block at offset 9, size 300, pts 0,
dts 0, duration 20, keyframe 1
demuxer -> ist_index:0 type:audio next_dts:13500 next_dts_time:0.0135
next_pts:13500 next_pts_time:0.0135 pkt_pts:1608 pkt_pts_time:0.0335
pkt_dts:1608 pkt_dts_time:0.0335 off:0 off_time:0
demuxer+ffmpeg -> ist_index:0 type:audio pkt_pts:1608 pkt_pts_time:0.0335
pkt_dts:1608 pkt_dts_time:0.0335 off:0 off_time:0
muxer <- type:audio pkt_pts:34 pkt_pts_time:0.034 pkt_dts:34
pkt_dts_time:0.034 size:174
[matroska @ 00000000005f76c0] Writing block at offset 316, size 165, pts
21, dts 21, duration 20, keyframe 1
demuxer -> ist_index:0 type:audio next_dts:33500 next_dts_time:0.0335
next_pts:33500 next_pts_time:0.0335 pkt_pts:2568 pkt_pts_time:0.0535
pkt_dts:2568 pkt_dts_time:0.0535 off:0 off_time:0
demuxer+ffmpeg -> ist_index:0 type:audio pkt_pts:2568 pkt_pts_time:0.0535
pkt_dts:2568 pkt_dts_time:0.0535 off:0 off_time:0
muxer <- type:audio pkt_pts:54 pkt_pts_time:0.054 pkt_dts:54
pkt_dts_time:0.054 size:173
[matroska @ 00000000005f76c0] Writing block at offset 488, size 174, pts
41, dts 41, duration 20, keyframe 1
demuxer -> ist_index:0 type:audio next_dts:53500 next_dts_time:0.0535
next_pts:53500 next_pts_time:0.0535 pkt_pts:3528 pkt_pts_time:0.0735
pkt_dts:3528 pkt_dts_time:0.0735 off:0 off_time:0
demuxer+ffmpeg -> ist_index:0 type:audio pkt_pts:3528 pkt_pts_time:0.0735
pkt_dts:3528 pkt_dts_time:0.0735 off:0 off_time:0
muxer <- type:audio pkt_pts:74 pkt_pts_time:0.074 pkt_dts:74
pkt_dts_time:0.074 size:320
[matroska @ 00000000005f76c0] Writing block at offset 669, size 173, pts
61, dts 61, duration 20, keyframe 1
No more output streams to write to, finishing.
[matroska @ 00000000005f76c0] Writing block at offset 849, size 320, pts
81, dts 81, duration 20, keyframe 1
[matroska @ 00000000005f76c0] end duration = 101
[matroska @ 00000000005f76c0] stream 0 end duration = 101
size= 2kB time=00:00:00.07 bitrate= 206.1kbits/s speed=10.3x
video:0kB audio:1kB subtitle:0kB other streams:0kB global headers:0kB
muxing overhead: 68.374557%
Input file #0 (sin.opus):
Input stream #0:0 (audio): 5 packets read (1132 bytes);
Total: 5 packets (1132 bytes) demuxed
Output file #0 (sin.mka):
Output stream #0:0 (audio): 5 packets muxed (1132 bytes);
Total: 5 packets (1132 bytes) muxed
0 frames successfully decoded, 0 decoding errors
[AVIOContext @ 00000000023b00c0] Statistics: 14 seeks, 10 writeouts
[AVIOContext @ 00000000005ff2a0] Statistics: 2007 bytes read, 0 seeks
}}}
--
Ticket URL: <https://trac.ffmpeg.org/ticket/6841#comment:5>
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