mjpeg stream

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mjpeg stream

Gabriel Zachmann
I would love to get some insights.

I have a video that contains 3 streams (see below for the full output of ffprobe).
This is causing me a bit of a headache.

My questions are:
-  what is Stream #0.2 ? is it the same video footage as Stream #0.0, except in a different codec ? why is it there?
-  can I just delete it, or is it necessary to view the video as a whole?
-  when converting the video (as a whole) , should I convert it , too, or just copy it? or can I safely omit it?
-  Can I assume that if there is a second video stream in a file, then it is usually not really needed?
-  If yes, can I assume that the second video stream is usually the one that could be omitted?
-  in Quicktime Player 7, I can see only one video track - why don't I see two tracks?

I would greatly appreciated all kinds of insights - I am not an expert in video formats.

IF you would like to look at the video for yourself, here it is:
   https://www.dropbox.com/s/f2ili147h1pn80v/Immersive%20Virtual%20Reality%20Anatomy%20Atlas%20V01.mp4?dl=0

Thanks a lot in advance.
Best regards, Gabriel


% ffprobe Immersive\ Virtual\ Reality\ Anatomy\ Atlas\ V01.mp4
ffprobe version 4.1 Copyright (c) 2007-2018 the FFmpeg developers
  built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)
  configuration: --prefix=/opt/local --enable-swscale --enable-avfilter --enable-avresample --enable-libmp3lame --enable-libvorbis --enable-libopus --enable-librsvg --enable-libtheora --enable-libopenjpeg --enable-libmodplug --enable-libvpx --enable-libsoxr --enable-libspeex --enable-libass --enable-libbluray --enable-lzma --enable-gnutls --enable-fontconfig --enable-libfreetype --enable-libfribidi --disable-libjack --disable-libopencore-amrnb --disable-libopencore-amrwb --disable-libxcb --disable-libxcb-shm --disable-libxcb-xfixes --disable-indev=jack --enable-opencl --disable-outdev=xv --enable-audiotoolbox --enable-videotoolbox --enable-sdl2 --disable-securetransport --mandir=/opt/local/share/man --enable-shared --enable-pthreads --cc=/usr/bin/clang --arch=x86_64 --enable-x86asm --enable-libx265 --enable-gpl --enable-postproc --enable-libx264 --enable-libxvid --enable-version3 --enable-libsmbclient --enable-nonfree --enable-libfdk-aac
  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
  libpostproc    55.  3.100 / 55.  3.100
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fa5ef80cc00] stream 0, timescale not set
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Immersive Virtual Reality Anatomy Atlas V01.mp4':
  Metadata:
    major_brand     : M4V
    minor_version   : 512
    compatible_brands: isomiso2avc1
    encoder         : Lavf56.36.100
  Duration: 00:01:10.47, start: 0.000000, bitrate: 3649 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 3502 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 127 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
    Stream #0:2: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 960x536 [SAR 144:144 DAR 120:67], 90k tbr, 90k tbn, 90k tbc




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Re: mjpeg stream

Carl Eugen Hoyos-2
2019-01-16 20:25 GMT+01:00, Gabriel Zachmann <[hidden email]>:
> I would love to get some insights.
>
> I have a video that contains 3 streams (see below for the full output of
> ffprobe).
> This is causing me a bit of a headache.
>
> My questions are:
> -  what is Stream #0.2

It is a low-quality sample frame from the original video,
you can extract it (for example) with:
$ ffmpeg -i input -map 0:2 -vcodec copy out.jpg

> ? is it the same video footage as Stream #0.0, except
> in a different codec ?

No, it is just one frame.

> why is it there?

Possibly to allow a peek into the content of the video.

> -  can I just delete it, or is it necessary to view the video as a whole?

You can not easily "delete" it because it part of a multimedia file
(that is typically non-trivial to edit) but it is not necessary and
if you create a new multimedia file with the same audio and same
video as your file, you can choose not to copy the still frame.
(In this case, you have not "deleted" it because you have created
a new file with certain different properties.)
Note that the single frame is 127k of 32M.

> -  when converting the video (as a whole) , should I convert it , too, or
> just copy it? or can I safely omit it?

You can omit it if you don't need it.

> -  Can I assume that if there is a second video stream in a file, then it is
> usually not really needed?

No, stereo presentations and presentations with a stream showing sheets
and another stream showing the presenter exist (for example).

> -  If yes, can I assume that the second video stream is usually the one that
> could be omitted?

> -  in Quicktime Player 7, I can see only one video track - why don't I see
> two tracks?

There should be directory viewers that should show you the still
frame instead of a general symbol.

Carl Eugen
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