[FFmpeg-trac] #2491(FFmpeg:new): audio stream start_time & duration overspan when encoding & split a video (-ss, -t)

[FFmpeg]

#2491: audio stream start_time & duration overspan when encoding & split a video
(-ss, -t)
-----------------------------------+---------------------------------------
             Reporter:  ronny1982  |                     Type:  enhancement
               Status:  new        |                 Priority:  minor
            Component:  FFmpeg     |                  Version:  git-master
             Keywords:             |               Blocked By:
             Blocking:             |  Reproduced by developer:  0
Analyzed by developer:  0          |
-----------------------------------+---------------------------------------
 I'm trying to extract and encode a segment of a video with a given start
 time and duration.

 Until version 0.10.7 the start time and duration of the extracted audio
 stream were almost accurate compared to the video stream.

 Since version 0.11.3 additional audio packets are appended that lies
 outside of the requested duration -> the audio stream is 'much' longer
 than the video stream compared to the result with version 0.10.7.

 Since version 1.1.4 the behavior changed again, the audio packets no
 longer starts with pts_time 0.0, instead they got an offset. This offset
 will also be added to the regular duration of the last audio packet.
 Technically the values belongs to the requested timespan:
 first_packet_pts_time + packet_duration > -ss <start_time>
 last packet_pts_time < -ss <start_time> + -t <duration>
 However the output of version 0.10.7 is more logical...

 Why making a fuss about 20~50ms additional difference between the stream
 durations? The higher accuracy (like in version 0.10.7) is required when
 you want to concatenate multiple segments, where different stream start
 times & durations playing an important role to prevent 'gaps' in the video
 stream (-> [http://code.google.com/p/ffmpegyag/issues/detail?id=2
 explained here])

 ----

 shell script for testing:
 {{{
 #!/bin/sh

 cd "$(dirname "$0")"

 # extract and encode segments with different ffmpeg versions
 ffmpeg-0.10.7 -i "Agnis Philosophy.mp4" -strict experimental -f mp4 -c:a
 aac -c:v mpeg4 -ss 00:00:11.000 -t 00:00:12.666 -y "agnis-part_0.10.7.mp4"
 ffmpeg-0.11.3 -i "Agnis Philosophy.mp4" -strict experimental -f mp4 -c:a
 aac -c:v mpeg4 -ss 00:00:11.000 -t 00:00:12.666 -y "agnis-part_0.11.3.mp4"
 ffmpeg-1.0.6 -i "Agnis Philosophy.mp4" -strict experimental -f mp4 -c:a
 aac -c:v mpeg4 -ss 00:00:11.000 -t 00:00:12.666 -y "agnis-part_1.0.6.mp4"
 ffmpeg-1.1.4 -i "Agnis Philosophy.mp4" -strict experimental -f mp4 -c:a
 aac -c:v mpeg4 -ss 00:00:11.000 -t 00:00:12.666 -y "agnis-part_1.1.4.mp4"
 ffmpeg-1.2 -i "Agnis Philosophy.mp4" -strict experimental -f mp4 -c:a aac
 -c:v mpeg4 -ss 00:00:11.000 -t 00:00:12.666 -y "agnis-part_1.2.mp4"

 # extract stream infos from each encoded segment
 ffprobe -show_streams 'agnis-part_0.10.7.mp4' | grep
 'STREAM\|start_time\|duration\|nb_frames' > 'info_0.10.7.txt'
 ffprobe -show_streams 'agnis-part_0.11.3.mp4' | grep
 'STREAM\|start_time\|duration\|nb_frames' > 'info_0.11.3.txt'
 ffprobe -show_streams 'agnis-part_1.0.6.mp4' | grep
 'STREAM\|start_time\|duration\|nb_frames' > 'info_1.0.6.txt'
 ffprobe -show_streams 'agnis-part_1.1.4.mp4' | grep
 'STREAM\|start_time\|duration\|nb_frames' > 'info_1.1.4.txt'
 ffprobe -show_streams 'agnis-part_1.2.mp4' | grep
 'STREAM\|start_time\|duration\|nb_frames' > 'info_1.2.txt'

 # extract packet infos from each encoded segment
 ffprobe -show_packets 'agnis-part_0.10.7.mp4' | grep
 'PACKET\|codec_type\|pts_time\|dts_time\|duration_time' >
 'packets_0.10.7.txt'
 ffprobe -show_packets 'agnis-part_0.11.3.mp4' | grep
 'PACKET\|codec_type\|pts_time\|dts_time\|duration_time' >
 'packets_0.11.3.txt'
 ffprobe -show_packets 'agnis-part_1.0.6.mp4' | grep
 'PACKET\|codec_type\|pts_time\|dts_time\|duration_time' >
 'packets_1.0.6.txt'
 ffprobe -show_packets 'agnis-part_1.1.4.mp4' | grep
 'PACKET\|codec_type\|pts_time\|dts_time\|duration_time' >
 'packets_1.1.4.txt'
 ffprobe -show_packets 'agnis-part_1.2.mp4' | grep
 'PACKET\|codec_type\|pts_time\|dts_time\|duration_time' >
 'packets_1.2.txt'
 }}}

 ----

 Taking a look into some selected stream infos of each encoded segment from
 ffprobe. You can notice the 'evolution' of the audio stream (first stream
 is video, second stream is audio):

 ||= '''ffmpeg-0.9.2 & ffmpeg-0.10.7''' =||= '''ffmpeg-0.11.3 &
 ffmpeg-1.0.6''' =||= '''fmpeg-1.1.4 & ffmpeg-1.2''' =||
 ||[STREAM]||[STREAM]||[STREAM]||
 ||start_time=0.000000||start_time=0.000000||start_time=0.000000||
 ||duration=12.666667||duration=12.666667||||duration=12.666667||
 ||nb_frames=380||nb_frames=380||nb_frames=380||
 ||{{{[/STREAM]}}}||{{{[/STREAM]}}}||{{{[/STREAM]}}}||
 ||[STREAM]||[STREAM]||[STREAM]||
 ||start_time=0.000000||start_time=0.000000||||start_time='''-0.016961'''||
 ||duration=12.678095||duration='''12.701315'''||duration='''12.701315'''||
 ||nb_frames=546||nb_frames='''547'''||nb_frames='''547'''||
 ||{{{[/STREAM]}}}||{{{[/STREAM]}}}||{{{[/STREAM]}}}||

 ----
 '''Source Video:'''
 * [http://ffmpegyag.googlecode.com/files/Agnis%20Philosophy.mp4 Agnis
 Philosophy.mp4 (134 MB)]
 '''Results:'''
 * [http://ffmpegyag.googlecode.com/files/agnis-part_0.10.7.mp4 Segment
 0.10.7 (3.5 MB)]
 * [http://ffmpegyag.googlecode.com/files/agnis-part_0.11.3.mp4 Segment
 0.11.3 (3.5 MB)]
 * [http://ffmpegyag.googlecode.com/files/agnis-part_1.0.6.mp4 Segment
 1.0.6 (3.5 MB)]
 * [http://ffmpegyag.googlecode.com/files/agnis-part_1.1.4.mp4 Segment
 1.1.4 (3.5 MB)]
 * [http://ffmpegyag.googlecode.com/files/agnis-part_1.2.mp4 Segment 1.2
 (3.5 MB)]
 * [http://ffmpegyag.googlecode.com/files/stream-packet-info.tar.gz Stream
 & Packet Infos tar.gz (34 KB)]

 *,,not sure if this behavior is a defect or is wanted by the developers,
 so setting the ticket to: enhancement with minor priority,,

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2491>
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