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• FFmpeg meaningful video thumbnails

  18 avril 2015, par Maverick

  I know this question has been discussed already here. However, it did not solve the problem completely. I trying to retrieve meaning thumbnails from video and while executing the following command.

  ffmpeg -ss 3 -i input.avi -vf "select=gt(scene\,0.4)" -frames:v 5 -vsync vfr -vf "fps=fps=1/600" out%02d.jpg

  As a result, I am only able to get 1 image out of this video. I am not sure, what is going wrong over here.

  Also, it would be great, if someone kindly give a quick explanation of this command parameters and filters. The command originally comes from here

  FFMPEG console output :

  ffmpeg version 2.6 Copyright (c) 2000-2015 the FFmpeg developers
  
    built with Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/2.6 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-libfreetype --enable-libtheora --enable-libvorbis --enable-libvpx --enable-librtmp --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libass --enable-ffplay --enable-libspeex --enable-libschroedinger --enable-libfdk-aac --enable-libopus --enable-frei0r --enable-libopenjpeg --disable-decoder=jpeg2000 --extra-cflags='-I/usr/local/Cellar/openjpeg/1.5.1_1/include/openjpeg-1.5 ' --enable-nonfree --enable-vda
  
    libavutil      54. 20.100 / 54. 20.100
  
    libavcodec     56. 26.100 / 56. 26.100
  
    libavformat    56. 25.101 / 56. 25.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 11.102 /  5. 11.102
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Input #0, avi, from 'tagesschau.avi':
  
    Metadata:
  
      encoder         : Lavf56.25.101
  
    Duration: 00:00:20.03, start: 0.000000, bitrate: 4357 kb/s
  
      Stream #0:0: Video: mpeg4 (Simple Profile) (xvid / 0x64697678), yuv420p, 720x540 [SAR 1:1 DAR 4:3], 4190 kb/s, 29.97 fps, 29.97 tbr, 29.97 tbn, 29.97 tbc
  
      Stream #0:1: Audio: ac3 ([0] [0][0] / 0x2000), 44100 Hz, stereo, fltp, 160 kb/s
  
  [swscaler @ 0x7fcb2a00f600] deprecated pixel format used, make sure you did set range correctly
  
  [mjpeg @ 0x7fcb2a803c00] bitrate tolerance 4000000 too small for bitrate 200000, overriding
  
  Output #0, image2, to 'out%02d.jpg':
  
    Metadata:
  
      encoder         : Lavf56.25.101
  
      Stream #0:0: Video: mjpeg, yuvj420p(pc), 720x540 [SAR 1:1 DAR 4:3], q=2-31, 200 kb/s, 0k fps, 0k tbn, 0k tbc
  
      Metadata:
  
        encoder         : Lavc56.26.100 mjpeg
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mpeg4 (native) -> mjpeg (native))
  
  Press [q] to stop, [?] for help
  
  frame=    1 fps=0.0 q=6.9 Lsize=N/A time=00:10:00.00 bitrate=N/A    
  
  video:44kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown 

• avcodec/vdpau : Support for VDPAU accelerated HEVC decoding

  13 juin 2015, par Philip Langdale

  avcodec/vdpau : Support for VDPAU accelerated HEVC decoding
  This change introduces basic support for HEVC decoding through vdpau.
  
  Right now, there are problems with the nvidia driver/library implementation
  
  that mean that frames are incorrectly laid out in memory when they are
  
  returned from the decoder, and it is normally impossible to recover the
  
  complete decoded frame due to loss of data from alignment inconsistencies.
  I obviously hope that nvidia will be fixing it in due course - I’ve verified
  
  the problems exist with their example application.
  As such, this support is not useful for any real world application, but I
  
  believe that it is correct (with the caveat that the mangled frames may hide
  
  problems) and will work properly once the nvidia problem is fixed.
  Right now it appears that any file encoded by x265 or nvenc is decoded
  
  correctly, but that’s because these files don’t use a bunch of HEVC
  
  features.
  Quick summary :
  Features that seem to work :
  1) Short Term References
  
  2) Scaling Lists
  
  3) Tiling
  Features with known problems :
  1) Long Term References
  It’s hard to tell what’s going on here. After I read the nvidia example
  
  app that does not set the IsLongTerm flag on LTRs, and changed my code,
  
  a bunch of frames using LTR started to display correctly, but there
  
  are still samples with glitches that are related to LTRs.
  In terms of real world files, both x265 and nvenc only use short term
  
  refs from this list. The divx encoder seems similar.
  Signed-off-by : Philip Langdale <philipl@overt.org>
  

  • [DH] configure
  • [DH] libavcodec/Makefile
  • [DH] libavcodec/allcodecs.c
  • [DH] libavcodec/hevc.c
  • [DH] libavcodec/vdpau_hevc.c
  • [DH] libavcodec/vdpau_internal.h

• How do I extract color matrix from MP4 an x264 stream in Media Foundation

  23 août 2016, par Jules

  I am playing a video (mp4 containing x264 encoded video stream) with a custom player using media foundation.

  When I convert the YUV information into RGB I need to account for the color matrix and range used at encode time.

  Some of my videos have this information, I can use MediaInfo.exe or FFMPEG to see that it is present.

  However, for such videos if I look at the relevant Media Foundation properties (Extended Color Information) the properties are not present in the files.

  So, somehow I need to find a way to access the information.

  Media Foundation does provide access to MF_MT_MPEG4_SAMPLE_DESCRIPTION and MF_MT_MPEG_SEQUENCE_HEADER for the video stream but I can’t find descriptions of what these contain.

  I noticed that the MF_MT_MPEG_SEQUENCE_HEADER is much longer for the videos with the information present and this (MPEG Headers Quick Reference) seems to suggest headers might contain the information I need.

  I’m looking for Color Range (limited/full), Color Primaries, Transfer Characteristics and Matrix Coefficients (BT.709 etc).

  I’d greatly appreciate any help finding this information from a Media Foundation video stream.

  Thanks

  Jules

  ---

  Update - Sequence Header

  The sequence header appears to be a subset of MPEG4 sample description, though I can’t find anything that indicates what either bits of data actually contains / doesn’t contain specifically.

  The sequence header appears to contain data structured as an MP4 byte stream as described in the H264 Standards Document and includes the VUI (Video Usability Information - Annex E of document) which may then include the colour information I’m interested in.

  Given that it’s a byte stream I need to know where it starts and whether there’s some existing code I could use to decode it.

  In FFMPEG in libavcodec/h264_ps.c there is a function called ff_h264_decode_seq_parameter_set which ends up calling decode_vui_parameters. It seems possible that seq_parameter_set maps to MF_MT_MPEG_SEQUENCE_HEADER and it may be possible to use that code to decode the data.

  If anyone one has any direct experience with decoding this data it would be very useful.

  Thanks again

  ---

  Update - Related posts

  I found this How to decode sprop-parameter-sets in a H264 SDP ? and Possible Locations for Sequence/Picture Parameter Set(s) for H.264 Stream which are fairly helpful.

  The sequence header would appear to be Sequence or picture parameter set (pps) and the parameters I want are the VUI extension subset.

  Plus this post H.264 stream structure gives the high level of how the stream data is structured, and the MF_MT_MPEG_SEQUENCE_HEADER appears to start with a NAL 0x00 0x00 0x01 so I’m guessing it is a NAL containing the PPS.