[FFmpeg-user] Why are half the frames "duplicate" ?

[sean darcy]

On 9/28/18 7:29 PM, Carl Eugen Hoyos wrote:
> 2018-09-28 20:58 GMT+02:00, sean darcy <seandarcy2 at gmail.com>:
> 
>> Also, I used ffprobe:
>>
>> ffprobe -show_frames -select_streams v -i in.mpg  2>&1 | grep -c
>> interlaced_frame=1
>> 2052
>> ffprobe -show_frames -select_streams v -i in.mpg  2>&1 | grep -c
>> interlaced_frame=0
>> 30347
>>
>> This means there are at least some interlaced frames
> 
> No, unfortunately ffprobe cannot tell you (the information above
> is mostly unrelated to the question if the content is interlaced,
> telecined or progressive).
> 
> Either use the idet filter or do a visual inspection.
> 
> Carl Eugen
> _______________________________________________

Never used idet filter before, so don't know how to make use of the info.

ffmpeg -vf idet -frames:v 5000 -an -f rawvideo -y /dev/null -i  in.mpg
ffmpeg version git-snapshot-20180928-RPMFusion Copyright (c) 2000-2018 
the FFmpeg developers
   built with gcc 8 (GCC)
   configuration: --prefix=/usr --bindir=/usr/bin 
--datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg 
--libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 
--optflags='-O2 -ffast-math -march=native -ftree-vectorize 
-fomit-frame-pointer -pipe -fPIC' --enable-bzlib --disable-crystalhd 
--enable-fontconfig --enable-frei0r --enable-gcrypt --enable-gnutls 
--enable-ladspa --enable-libass --enable-libbluray --enable-libcdio 
--enable-libfdk-aac --enable-nonfree --enable-indev=jack 
--enable-libfreetype --enable-libfribidi --enable-libgsm 
--enable-libmp3lame --enable-openal --enable-opencl --disable-libopencv 
--enable-opengl --enable-libopenjpeg --enable-libopus --enable-libpulse 
--enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvorbis 
--enable-libv4l2 --enable-libvpx --enable-libwebp --enable-libx264 
--enable-libx265 --enable-avfilter --enable-postproc --enable-pthreads 
--disable-static --enable-shared --enable-gpl --enable-version3 
--enable-nonfree --disable-debug --enable-stripping 
--shlibdir=/usr/lib64 --enable-runtime-cpudetect
   libavutil      56. 19.101 / 56. 19.101
   libavcodec     58. 31.101 / 58. 31.101
   libavformat    58. 18.103 / 58. 18.103
   libavdevice    58.  4.104 / 58.  4.104
   libavfilter     7. 33.100 /  7. 33.100
   libswscale      5.  2.100 /  5.  2.100
   libswresample   3.  2.100 /  3.  2.100
   libpostproc    55.  2.100 / 55.  2.100
[mpeg2video @ 0x1eef200] Invalid frame dimensions 0x0.
     Last message repeated 10 times
Input #0, mpeg, from 'in.mpg':
   Duration: 26:09:34.50, start: 1305.384367, bitrate: 91 kb/s
     Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, 
progressive), 720x480 [SAR 8:9 DAR 4:3], Closed Captions, 29.97 fps, 
59.94 tbr, 90k tbn, 59.94 tbc
     Stream #0:1[0x81]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s
     Stream #0:2[0x80]: Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s
     Stream #0:3[0x1bf]: Data: dvd_nav_packet
     Stream #0:4[0x22]: Subtitle: dvd_subtitle
     Stream #0:5[0x21]: Subtitle: dvd_subtitle
     Stream #0:6[0x20]: Subtitle: dvd_subtitle
Stream mapping:
   Stream #0:0 -> #0:0 (mpeg2video (native) -> rawvideo (native))
Press [q] to stop, [?] for help
Output #0, rawvideo, to '/dev/null':
   Metadata:
     encoder         : Lavf58.18.103
     Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 720x480 
[SAR 8:9 DAR 4:3], q=2-31, 124291 kb/s, 29.97 fps, 29.97 tbn, 29.97 tbc
     Metadata:
       encoder         : Lavc58.31.101 rawvideo
More than 1000 frames duplicated= 2191360kB time=00:02:24.44 
bitrate=124280.6kbits/s dup=867 drop=0 speed=72.2x
frame= 5000 fps=2162 q=-0.0 Lsize= 2531250kB time=00:02:46.83 
bitrate=124291.7kbits/s dup=1001 drop=0 speed=72.1x
video:2531250kB audio:0kB subtitle:0kB other streams:0kB global 
headers:0kB muxing overhead: 0.000000%
[Parsed_idet_0 @ 0x21f7dc0] Repeated Fields: Neither:  4000 Top:     0 
Bottom:     0
[Parsed_idet_0 @ 0x21f7dc0] Single frame detection: TFF:     0 BFF: 
0 Progressive:  3894 Undetermined:   106
[Parsed_idet_0 @ 0x21f7dc0] Multi frame detection: TFF:     0 BFF:     0 
Progressive:  4000 Undetermined:     0

As I read this, the idet filter only saw 4000 out of the 5000 frames, of 
which 106 couldn't be classified. What about the 1001 duplicated frames ?

Again, thanks for the help.