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• avcodec/v4l2 : set sizeimage param for non-raw buffers [fixes #6716]

  4 octobre 2017, par Jorge Ramirez-Ortiz

  avcodec/v4l2 : set sizeimage param for non-raw buffers [fixes #6716]
  Some V4L2 drivers fail to allocate buffers when sizeimage is not set
  
  to a max value. This is indeed the case for s5p-mfc [1]
  Most drivers should be able to calculate this value from the frame
  
  dimensions and format - or at least have their own default.
  However since this work around should not impact those drivers doing
  
  the "right thing" this commit just provides such a default.
  The calculations were extracted from the v4l2 driver used to develop
  
  the ffmpeg v4l2_m2m support [2]. See venc.c and vdec.c
  [1] linux.git/drivers/media/platform/s5p-mfc
  
  [2] linux.git/drivers/media/platform/qcom/venus/
  

  • [DH] libavcodec/v4l2_context.c

• confused about lhls in ffmpeg

  27 décembre 2020, par JohnL

  I am more than a little confused about trying to use the experimental lhls option in ffmpeg.

  


  I have built ffmpeg from source (which takes a while), and currently have version 4.1.6 running.

  


  Reading other threads here, and the ffmpeg docs, it appears that the lhls option is available only in the Dash muxer.

  


  I gravitated to HLS because of its support in Apple devices, and I thought that lhls was related (and Apple was drafting the spec).

  


  Then there is the comment in the ffmpeg docs that states that the hls.js folks are working on supporting lhls in their library, which I also use to support browsers like Chrome.

  


  Should I be using dash instead of hls for my prototype ? I want to try and get very low latency for a construction inspection app I am considering building. Right now, the latency I am seeing is 10-15 seconds.

  


  Any insights would be appreciated. TIA

  


  See my comment below. I have many of the dash format flags working, but can't get -lhls to work. Here are some of the build flags used :

  


  conversion : avcodec configuration : —prefix=/usr —extra-version='1 deb10u1+rpt1' —toolchain=hardened —incdir=/usr/include/arm-linux-gnueabihf —enable-gpl —disable-stripping —enable-avresample —disable-filter=resample —enable-avisynth —enable-gnutls —enable-ladspa —enable-libaom —enable-libass —enable-libbluray —enable-libbs2b —enable-libcaca —enable-libcdio —enable-libcodec2 —enable-libflite —enable-libfontconfig —enable-libfreetype —enable-libfribidi —enable-libgme —enable-libgsm —enable-libjack —enable-libmp3lame —enable-libmysofa —enable-libopenjpeg —enable-libopenmpt —enable-libopus —enable-libpulse —enable-librsvg —enable-librubberband —enable-libshine —enable-libsnappy —enable-libsoxr —enable-libspeex —enable-libssh —enable-libtheora —enable-libtwolame —enable-libvidstab —enable-libvorbis —enable-libvpx —enable-libwavpack —enable-libwebp —enable-libx265 —enable-libxml2 —enable-libxvid —enable-libzmq —enable-libzvbi —enable-lv2 —enable-omx —enable-openal —enable-opengl —enable-sdl2 —enable-omx-rpi —enable-mmal —enable-neon —enable-rpi —enable-libdc1394 —enable-libdrm —enable-libiec61883 —enable-chromaprint —enable-frei0r —enable-libx264 —libdir=/usr/lib/arm-linux-gnueabihf/neon/vfp —cpu=cortex-a7 —arch=armv6t2 —disable-thumb —enable-shared —disable-doc —disable-programs

  


• ffmpeg does not recognize long string filter in execv

  4 mai 2023, par incertia

  I am writing some simple python script to call ffmpeg and concat some clips together. However, it doesn't work for reasons I am unable to explain.

  


  below is a working version of the code after some debugging

  


  inputs = sorted(list(askopenfilenames()))
n = len(inputs)

filter = []
for i in range(n):
    filter.append("[{}:v]".format(i))
    filter.append("[{}:a]".format(i))
filter.append("concat={}:v=1:a=1".format(n))
filter.append("[v]")
filter.append("[a]")
filter = " ".join(filter)

fargs = zip(itertools.repeat('-i'), inputs)
fargs = itertools.chain(
    ["ffmpeg"],
    itertools.chain.from_iterable(fargs),
    ["-filter_complex", '"{}"'.format(filter), "-vsync", "vfr", "-map", "[v]", "-map", "[a]"],
    ["-c:v", "libx264", "-crf", "{}".format(quality)],
    ["-c:a", "aac", "-b:a", "192k"],
    [out]
    )

os.execvp("ffmpeg", list(fargs))


  


  but the entire fargs construction causes ffmpeg to complain about the filter chain when quotes are not utilized. e.g. by utilizing the below process

  


  fargs = itertools.chain(
    ["ffmpeg", "-loglevel", "debug"],
    itertools.chain.from_iterable(fargs),
    #["-filter_complex", '"{}"'.format(filter), "-vsync", "vfr", "-map", "[v]", "-map", "[a]"],
    ["-filter_complex", filter, "-vsync", "vfr", "-map", "[v]", "-map", "[a]"],
    ["-c:v", "libx264", "-crf", "{}".format(quality)],
    ["-c:a", "aac", "-b:a", "192k"],
    [out]
    )


  


  we see that ffmpeg somehow sees this as multiple arguments

  


  Reading option '-filter_complex' ... matched as option 'filter_complex' (create a complex filtergraph) with argument '[0:v]'.
Reading option '[0:a]' ... matched as output url.
Reading option '[1:v]' ... matched as output url.
Reading option '[1:a]' ... matched as output url.
Reading option '[2:v]' ... matched as output url.
Reading option '[2:a]' ... matched as output url.
Reading option 'concat=3:v=1:a=1' ... matched as output url.
Reading option '[v]' ... matched as output url.
Reading option '[a]' ... matched as output url.


  


  even though a simple print(list(fargs)) yields

  


  ['ffmpeg', '-loglevel', 'debug', '-i', 'a.mp4', '-i', 'b.mp4', '-i', 'c.mp4', '-filter_complex', '[0:v] [0:a] [1:v] [1:a] [2:v] [2:a] concat=3:v=1:a=1 [v] [a]', '-vsync', 'vfr', '-map', '[v]', '-map', '[a]', '-c:v', 'libx264', '-crf', '20', '-c:a', 'aac', '-b:a', '192k', 'asdf.mp4']


  


  implying that the long filter string is being passed to ffmpeg as a single argument.