[FFmpeg-trac] #6306(undetermined:new): Wrong first frame using new decode API

[FFmpeg]

#6306: Wrong first frame using new decode API
-------------------------------------+-------------------------------------
             Reporter:  s0m3         |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:
              Version:  unspecified  |  undetermined
             Keywords:               |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  1
-------------------------------------+-------------------------------------

Comment (by s0m3):

 {{{
 D:\>"D:\ffmpeg-3.2.4-win32-shared\bin\ffprobe.exe" -i "D:\Samples\The
 Simpsons Movie - 1080p Trailer.mp4"
 ffprobe version 3.2.4 Copyright (c) 2007-2017 the FFmpeg developers
   built with gcc 6.3.0 (GCC)
 <snip>
 [mov,mp4,m4a,3gp,3g2,mj2 @ 004772e0] stream 0, timescale not set
 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'D:\Samples\The Simpsons Movie -
 1080p Trailer.mp4':
   Metadata:
     major_brand     : isom
     minor_version   : 1
     compatible_brands: isomavc1
     creation_time   : 2007-07-17T09:18:37.000000Z
     genre           : Trailer
     artist          : Fox
     title           : The Simpsons Movie
     date            : 2007
   Duration: 00:02:17.25, start: 0.000000, bitrate: 8591 kb/s
     Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p,
 1920x800,
  8486 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
     Metadata:
       creation_time   : 2007-07-17T09:18:37.000000Z
       handler_name    : GPAC ISO Video Handler
     Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, 5.1,
 fltp,
 107 kb/s (default)
     Metadata:
       creation_time   : 2007-07-17T09:18:45.000000Z
       handler_name    : GPAC ISO Audio Handler
     Stream #0:2: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown),
 101x150 [S
 AR 72:72 DAR 101:150], 90k tbr, 90k tbn, 90k tbc
 }}}

 The file has 3 streams. Stream #0:0 is the video part, #0:1 the audio part
 and #0:2 is an embedded picture ("cover art" as VLC calls it).


 {{{
 D:\>"D:\ffmpeg-3.2.4-win32-shared\bin\ffprobe.exe" -i "D:\Samples\The
 Simpsons Movie - 1080p Trailer.mp4" -show_frames
 <output cut to only keep 4 frames of stream 0>
 [FRAME]
 media_type=video
 stream_index=0
 key_frame=1
 pkt_pts=2002
 pkt_pts_time=0.083417
 pkt_dts=2002
 pkt_dts_time=0.083417
 best_effort_timestamp=2002
 best_effort_timestamp_time=0.083417
 pkt_duration=1001
 pkt_duration_time=0.041708
 pkt_pos=71545
 pkt_size=65391
 <snip>
 [/FRAME]
 [FRAME]
 media_type=video
 stream_index=0
 key_frame=0
 pkt_pts=3003
 pkt_pts_time=0.125125
 pkt_dts=3003
 pkt_dts_time=0.125125
 best_effort_timestamp=3003
 best_effort_timestamp_time=0.125125
 pkt_duration=1001
 pkt_duration_time=0.041708
 pkt_pos=137164
 pkt_size=56
 <snip>
 [/FRAME]
 [FRAME]
 media_type=video
 stream_index=0
 key_frame=0
 pkt_pts=4004
 pkt_pts_time=0.166833
 pkt_dts=4004
 pkt_dts_time=0.166833
 best_effort_timestamp=4004
 best_effort_timestamp_time=0.166833
 pkt_duration=1001
 pkt_duration_time=0.041708
 pkt_pos=137103
 pkt_size=61
 <snip>
 [/FRAME]
 [FRAME]
 media_type=video
 stream_index=0
 key_frame=0
 pkt_pts=5005
 pkt_pts_time=0.208542
 pkt_dts=5005
 pkt_dts_time=0.208542
 best_effort_timestamp=5005
 best_effort_timestamp_time=0.208542
 pkt_duration=1001
 pkt_duration_time=0.041708
 pkt_pos=136936
 pkt_size=167
 <snip>
 }}}

 So on ffmpeg side, start time is 0.083417 as shown with the following
 excerpt:


 {{{
 D:\>"D:\ffmpeg-3.2.4-win32-shared\bin\ffprobe.exe" -i "D:\Samples\The
 Simpsons Movie - 1080p Trailer.mp4" -show_streams
 [STREAM]
 index=0
 <snip>
 timecode=N/A
 <snip>
 start_pts=2002
 start_time=0.083417
 <snip>
 }}}

 But with StreamEye v3.1, I have:

 {{{
 stream=0, display=0, size=65391, type=I, key=yes, offset=0x11779,
 time=00:00:00.000
 stream=1, display=3, size=  167, type=P, key= no, offset=0x216e8,
 time=00:00:00.125
 stream=2, display=2, size=   61, type=B, key= no, offset=0x2178f,
 time=00:00:00.083
 stream=3, display=1, size=   56, type=B, key= no, offset=0x217cc,
 time=00:00:00.041
 }}}


 If you look at size and offset of each frame, we're talking about the same
 ones but their timestamps differ.
 ffmpeg start timecode is frame 3 timestamp, not the first one (if
 StreamEye is correct).

 I do think decoded frames are ok but their associated timestamp is not.
 My question is: who's right? Is first frame timestamp 0 or 0.083417 ?

--
Ticket URL: <https://trac.ffmpeg.org/ticket/6306#comment:3>
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