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  • FFmpeg/Libav LZW compression

    1er avril 2016, par Sir DrinksCoffeeALot

    I'm trying to implement libav's LZW compression and decompression methods into my own project since the code is already there and i don't have to invent anything new (i'm using LZW just to test how much can i compress video before sending it through LAN).

    I'm not quite sure if i'm doing something wrong since their code is quite complex (at some point they are shifting bits and such), and some parts i can't really understand. But anyways, here is what i have tried so far.

    I've allocated/initialized few buffers (input/output), LZWEncodeState and LZWState structures. After that i've called function that fills up LZWEncodeState structure with some default values (ff_lzw_encode_init), and after that i called ff_lzw_encode and passed LZWEncodeState reference together with input buffer and it's size. That's what iv'e done encoding-part wise.

    For the decode part, we have to call ff_lzw_encode_open which basicly allocates LZWState structure memory, ff_lzw_decode_init (fills LZWState with default/passed valued) and after that, we use ff_lzw_decode to decode buffer back into original one (since LZW should be lossless).

    The thing is that after encoding/decoding, in output buffer only first 2 values are same as those in input buffer. I have no idea why is that happening. I've tried different values, but nothing has changed. So if anyone else experienced these kind of problems, and figured how to solve them, please let me know or try to explain why is that happening.

  • why is this intel hardware accellerated transcoding in ffmpeg not working ?

    1er avril 2016, par Jabb

    I compiled ffmpeg with intel hardware accelleration, but I cannot transcode the simpsons 720p video from http://www.h264info.com/clips.html with success.

    this is the error I get:

    Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

    and this is the full output from ffmpeg. What could be wrong?

    root@ubuntu:/tmp# ffmpeg -i test.mp4 -vcodec h264_qsv out1.yuv
ffmpeg version N-79177-ga677121 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.1)
  configuration: --prefix=/root/ffmpeg_build --pkg-config-flags=--static --extra-cflags=-I/root/ffmpeg_build/include --extra-ldflags=-L/root/ffmpeg_build/lib --bindir=/root/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree --enable-libmfx
  libavutil      55. 19.100 / 55. 19.100
  libavcodec     57. 32.100 / 57. 32.100
  libavformat    57. 29.101 / 57. 29.101
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 40.102 /  6. 40.102
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 1
    compatible_brands: isomavc1
    creation_time   : 2007-02-19 05:03:04
  Duration: 00:02:17.30, start: 0.000000, bitrate: 4283 kb/s
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1280x544, 4221 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)
    Metadata:
      creation_time   : 2007-02-19 05:03:04
      handler_name    : GPAC ISO Video Handler
    Stream #0:1(und): Audio: aac (HE-AAC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 64 kb/s (default)
    Metadata:
      creation_time   : 2007-02-19 05:03:08
      handler_name    : GPAC ISO Audio Handler
[h264_qsv @ 0x2f626a0] Error initializing an internal MFX session
Output #0, rawvideo, to 'out1.yuv':
  Metadata:
    major_brand     : isom
    minor_version   : 1
    compatible_brands: isomavc1
    Stream #0:0(und): Video: h264, none, q=2-31, 128 kb/s, 23.98 fps (default)
    Metadata:
      creation_time   : 2007-02-19 05:03:04
      handler_name    : GPAC ISO Video Handler
      encoder         : Lavc57.32.100 h264_qsv
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (h264_qsv))
Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height

  • Rotate image with ffmpeg

    1er avril 2016, par Prateek

    I just figure out how to rotate image with FFmpeg. But issue is when Filename contain "%" sign. Then that command not work.

    ffmpeg -y -i '/mypath/Prat%eek.jpg' -vf transpose=2 '/mypath/Prat%eek.jpg'

  • How does subtitle hardcoding works in ffmpeg ?

    1er avril 2016, par Ketan Kulkarni

    The manual for the same is available on: http://superuser.com/questions/838072/ffmpeg-hardcoding-burning-filename-in-video https://trac.ffmpeg.org/wiki/HowToBurnSubtitlesIntoVideo

    Sample command is: ffmpeg -i video.avi -vf subtitles=subtitle.srt out.avi

  • How does subtitle hardcoding work in ffmpeg ?

    1er avril 2016, par Ketan Kulkarni

    The manual for the same is available on: http://superuser.com/questions/838072/ffmpeg-hardcoding-burning-filename-in-video https://trac.ffmpeg.org/wiki/HowToBurnSubtitlesIntoVideo

    Sample command is: ffmpeg -i video.avi -vf subtitles=subtitle.srt out.avi

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