[FFmpeg-user] Pipe concat doubles frame rate (was: Re: Duplicated frames warnings when processing video) after pipe concatenation but not when processing source files

[Joel Roth]

Joel Roth wrote:
> Following up my own post.
> 
> Joel Roth wrote:
> > Hi list,
> > 
> > First of all, thanks to the ffmpeg developers and community
> > for this awesome software.
> > 
> > I'm using a two-pass workflow, where I pipe concatenate
> > source files in the first pass, then trim and process the
> > result in a second pass.  I am not changing framerates. 
> > 
> > Quoting from https://video.stackexchange.com/questions/20958/ffmpeg-dropping-duplicate-frames
> > 
> >     FFmpeg duplicates or drops frames when the input and output framerates differ. 
> > 
> > If I apply an ffmpeg command line to process a raw MTS file
> > from a camera, I do not get "More than 1000 frames duplicated"
> > warnings during processing.
> > 
> > However if I combine MTS files using pipe concatenation,
> > e.g.
> > 
> >     ffmpeg -i concat:"./00000.MTS|./00001.MTS" -codec copy ./00000.mp4
> > 
> > then run the same command line on the mp4 result, I get
> > plentiful duplicate frame warnings.
> > 
> > I'm using Jon Van Sickle's statically ffmpeg, to wit, ffmpeg-git-20180216-64bit-static/ffmpeg
> > from https://www.johnvansickle.com/ffmpeg/
> > 
> > The command line is:
> > 
> >     ffmpeg -i ./00000.mp4 -to 3:31 -c:v libx264 -preset:v medium -profile:v main -tune:v film -s:v 640x360 -c:a aac -b:a 80k -ac 2 -ar 24000 -level 3 -strict -2 -copyts  -ss 1:29 ../final/20180220-1.mp4
> 
> According to ffprobe, the frame rate of the pipe-concatenated video is double.
> 
> 
> ffprobe version N-45077-g8a8d0b319-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2007-2018 the FFmpeg developers
>   built with gcc 6.3.0 (Debian 6.3.0-18) 20170516
>   configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc-6 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gray --enable-libfribidi --enable-libass --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libzimg
>   libavutil      56.  7.101 / 56.  7.101
>   libavcodec     58. 11.101 / 58. 11.101
>   libavformat    58.  9.100 / 58.  9.100
>   libavdevice    58.  1.100 / 58.  1.100
>   libavfilter     7. 12.100 /  7. 12.100
>   libswscale      5.  0.101 /  5.  0.101
>   libswresample   3.  0.101 /  3.  0.101
>   libpostproc    55.  0.100 / 55.  0.100
> Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '00000.mp4':
>   Metadata:
>     major_brand     : isom
>     minor_version   : 512
>     compatible_brands: isomiso2avc1mp41
>     encoder         : Lavf58.9.100
>   Duration: 00:58:26.02, start: 0.000000, bitrate: 6903 kb/s
>     Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1440x1080 [SAR 4:3 DAR 16:9], 6637 kb/s, 59.94 fps, 59.94 tbr, 90k tbn, 59.94 tbc (default)
>     Metadata:
>       handler_name    : VideoHandler
>     Stream #0:1(und): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 256 kb/s (default)
>     Metadata:
>       handler_name    : SoundHandler
>     Side data:
>       audio service type: main
>  /mnt/ba1/buenos-aires-1/20180220/raw $ ffprobe *0.MTS
> ffprobe version N-45077-g8a8d0b319-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2007-2018 the FFmpeg developers
>   built with gcc 6.3.0 (Debian 6.3.0-18) 20170516
>   configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc-6 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gray --enable-libfribidi --enable-libass --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libzimg
>   libavutil      56.  7.101 / 56.  7.101
>   libavcodec     58. 11.101 / 58. 11.101
>   libavformat    58.  9.100 / 58.  9.100
>   libavdevice    58.  1.100 / 58.  1.100
>   libavfilter     7. 12.100 /  7. 12.100
>   libswscale      5.  0.101 /  5.  0.101
>   libswresample   3.  0.101 /  3.  0.101
>   libpostproc    55.  0.100 / 55.  0.100
> Input #0, mpegts, from '00000.MTS':
>   Duration: 00:37:25.73, start: 0.800300, bitrate: 7279 kb/s
>   Program 1
>     Stream #0:0[0x1011]: Video: h264 (High) (HDMV / 0x564D4448), yuv420p(top first), 1440x1080 [SAR 4:3 DAR 16:9], 29.97 fps, 59.94 tbr, 90k tbn, 59.94 tbc
>     Stream #0:1[0x1100]: Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 256 kb/s
>  

By adding the -r argument with the correct frame rate in the
second pass, I avoid the duplicate frame warnings. 

The doubled frame rate using pipe concat appears to be a
bug.

cheers


-- 
Joel Roth