[FFmpeg-trac] #6676(avcodec:new): mpeg2 decoder always output some redundant dummy frames for interlace videos

FFmpeg trac at avcodec.org
Thu Sep 21 10:22:37 EEST 2017


#6676: mpeg2 decoder always output some redundant dummy frames for interlace
videos
-------------------------------------+-------------------------------------
             Reporter:  lizhong1008  |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  avcodec      |                  Version:  git-
             Keywords:  mpeg2        |  master
  decoder                            |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 If a mpeg2 video is a field video, ffmpeg will always insert a dummy frame
 when decoding the first key filed picture. And the dummy frame will be
 output later.
 Take the attachment file (tcela-8-fp-dp.bits.mpeg2) as example, this clip
 has 4 frames (8 fields), but 5 frames will be output after decoding, the
 first output frame is a redundant dummy frame.

 How to reproduce:
 ffmpeg -i /root/Videos/yami_mpeg2/tcela-8-fp-dp.bits.mpeg2 -pix_fmt
 yuv420p /root/Videos/tcela-8-fp-dp.bits.mpeg_sw_720x480.yuv
 ffmpeg version N-87349-g0426e77108 Copyright (c) 2000-2017 the FFmpeg
 developers
   built with gcc 6.3.0 (Ubuntu 6.3.0-12ubuntu2) 20170406
   configuration: --prefix=/opt/X11R7/ --enable-vaapi --enable-libx264
 --enable-libx265 --enable-gpl --disable-optimizations --enable-debug=3
   libavutil      55. 75.100 / 55. 75.100
   libavcodec     57.106.101 / 57.106.101
   libavformat    57. 82.101 / 57. 82.101
   libavdevice    57.  8.101 / 57.  8.101
   libavfilter     6.105.100 /  6.105.100
   libswscale      4.  7.103 /  4.  7.103
   libswresample   2.  8.100 /  2.  8.100
   libpostproc    54.  6.100 / 54.  6.100
 [mpegvideo @ 0x557bd94c37e0] Estimating duration from bitrate, this may be
 inaccurate
 Input #0, mpegvideo, from '/root/Videos/yami_mpeg2/tcela-8-fp-
 dp.bits.mpeg2':
   Duration: 00:00:00.15, bitrate: 15000 kb/s
     Stream #0:0: Video: mpeg2video (Main), yuv420p(tv, bottom first),
 720x480 [SAR 8:9 DAR 4:3], 15000 kb/s, 30 fps, 30 tbr, 1200k tbn, 60 tbc
 Stream mapping:
   Stream #0:0 -> #0:0 (mpeg2video (native) -> rawvideo (native))
 Press [q] to stop, [?] for help
 Output #0, rawvideo, to '/root/Videos/tcela-8-fp-
 dp.bits.mpeg_sw_720x480.yuv':
   Metadata:
     encoder         : Lavf57.82.101
     Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 720x480
 [SAR 8:9 DAR 4:3], q=2-31, 124416 kb/s, 30 fps, 30 tbn, 30 tbc
     Metadata:
       encoder         : Lavc57.106.101 rawvideo
 frame=    5 fps=0.0 q=-0.0 Lsize=    2531kB time=00:00:00.16
 bitrate=124415.8kbits/s speed=18.1x
 video:2531kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.000000%

--
Ticket URL: <https://trac.ffmpeg.org/ticket/6676>
FFmpeg <https://ffmpeg.org>
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