[FFmpeg-user] MTS to MP4 lossless conversion issues

[Moritz Barsnick]

On Mon, Jul 10, 2017 at 15:03:49 +0200, Nick Gilmour wrote:
> *track 1: codec frame size is not set*
> 1. I googled also about this but I still don't know what does that mean and
> how I should deal with it. Is it an error or should I change something?

It about the audio track and I think it shouldn't matter. (I don't know
absolutely for sure though.)

> 2. I also see with VLC > Tools > Codec Information that the output file has
> 25 frames per sec, whereas the input file has 50 frames per sec. This
> although the output of the previous command shows 50 fps for the output
> file. So what is going on? Is VLC wrong? How can I get the 50 fps in the
> output file? Do 25 fps less mean reduced quality?

If you copy the stream ("-c[:x] copy"), no quality is reduced.

VLC may be wrong. See this (from the input):
>     Stream #0:0[0x1011]: Video: h264 (High) (HDMV / 0x564D4448), yuv420p(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], 50 fps, 25 tbr, 90k tbn, 100 tbc

"50 fps" is the frame rate given by the demuxer, "25 tbr" is the frame
rate guessed (by ffmpeg) from actual packets' timestamps. If you dump
all frames' info with ffprobe, we could double-check this conclusion.

I don't understand why VLC sees differences in the two files though. It
would be interesting to see what the container vs. stream metadata
says. It could be ffmpeg is adding info to the MP4 which the MTS just
didn't have (because it e.g. only has per-stream metadata). Or
something like that.

What is the output of
$ ffmpeg -i 00000.ffmpeg1.mp4
??

Can you provide such an MTS sample? (As short as possibly, but able to
reproduce the issue.)

> 3. The AVCHD format comes also with other files except MTS e.g. CPI. Are
> these important for the conversion or for use with video editing tools
> like Kdenlive?

The CPI file apparently holds extra metadata, but ffmpeg can't make use
of it. Final Cut Pro and iMovie apparently can. (I keep writing
"apparently", because I googled. Did you?
http://www.pavtube.com/avchd-cpi-file-format.html)

>     Stream #0:2[0x1200]: Subtitle: hdmv_pgs_subtitle ([144][0][0][0] / 0x0090), 1280x720

Subtitles? Interesting, what do they contain? :)

> Regards
> Nick

Cheers,
Moritz


> $ ffmpeg -i 00000.MTS -vcodec copy -acodec copy -sn 00000.ffmpeg1.mp4
> ffmpeg version 3.3.2-1~16.04.york1 Copyright (c) 2000-2017 the FFmpeg developers
>   built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
>   configuration: --prefix=/usr --extra-version='1~16.04.york1' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
>   libavutil      55. 58.100 / 55. 58.100
>   libavcodec     57. 89.100 / 57. 89.100
>   libavformat    57. 71.100 / 57. 71.100
>   libavdevice    57.  6.100 / 57.  6.100
>   libavfilter     6. 82.100 /  6. 82.100
>   libavresample   3.  5.  0 /  3.  5.  0
>   libswscale      4.  6.100 /  4.  6.100
>   libswresample   2.  7.100 /  2.  7.100
>   libpostproc    54.  5.100 / 54.  5.100
> Input #0, mpegts, from '00000.MTS':
>   Duration: 00:00:15.10, start: 0.888889, bitrate: 13700 kb/s
>   Program 1 
>     Stream #0:0[0x1011]: Video: h264 (High) (HDMV / 0x564D4448), yuv420p(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], 50 fps, 25 tbr, 90k tbn, 100 tbc
>     Stream #0:1[0x1100]: Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 192 kb/s
>     Stream #0:2[0x1200]: Subtitle: hdmv_pgs_subtitle ([144][0][0][0] / 0x0090), 1280x720
> [mp4 @ 0x55a37b91a4a0] track 1: codec frame size is not set
> Output #0, mp4, to '00000.ffmpeg1.mp4':
>   Metadata:
>     encoder         : Lavf57.71.100
>     Stream #0:0: Video: h264 (High) ([33][0][0][0] / 0x0021), yuv420p(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 50 fps, 25 tbr, 90k tbn, 90k tbc
>     Stream #0:1: Audio: ac3 ([165][0][0][0] / 0x00A5), 48000 Hz, stereo, fltp, 192 kb/s
> Stream mapping:
>   Stream #0:0 -> #0:0 (copy)
>   Stream #0:1 -> #0:1 (copy)
> Press [q] to stop, [?] for help
> frame=  377 fps=0.0 q=-1.0 Lsize=   23852kB time=00:00:15.07 bitrate=12964.2kbits/s speed= 247x    
> video:23490kB audio:354kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.033670%

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