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• bytestream : Make get_bytes_left compatible with overread

  14 décembre 2019, par Andreas Rheinhardt

  bytestream : Make get_bytes_left compatible with overread
  bytestream2_get_bytes_left returns an unsigned int ; as a result,
  
  it returns big positive numbers if an overread already happened,
  
  making it unsuitable for scenarios where one wants to allow this
  
  in a controlled way (because the buffer is actually padded so that
  
  no segfaults can happen). So change it to return an ordinary int.
  Also, bytestream2_get_bytes_left_p has been modified in the same way.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/bytestream.h

• encoding by using ffmpeg library

  22 août 2013, par Mustafe

  I am currently developing an application by using ffmpeg library. I have a problem with encoding pcm/raw datas. In ffmpeg/encoding_decoding.c source code, at line 146 in this function :

  buffer_size = av_samples_get_buffer_size(NULL, c->channels, c->frame_size, c->sample_fmt, 0);

  buffer_size is being calculated. My function always returns -22 which states an error. After a little examanation I noticed that in line 1888 at avcodec.h it is stated as following which shows the reason. Since CODEC_CAP_VARIABLE_FRAME_SIZE is set my function returns -22 and my program terminates. In this case the encoding code example in ffmpeg's website also could not work. How can I solve this problem ?

  encoding: set by libavcodec in avcodec_open2(). Each submitted frame except the last must contain exactly frame_size samples per channel. May be 0 when the codec has CODEC_CAP_VARIABLE_FRAME_SIZE set, then the frame size is not restricted. decoding: may be set by some decoders to indicate constant frame size

• understand what is the GOP size (i-frame/p-frame ratio) in a video

  29 avril 2012, par nkint

  i am doing stuffs with a video in action script and i need to seek a video to acertain frame. according to the reference, using NetStream.seek i can seek only to the nearest k-frame :

  Seeks the keyframe (also called an I-frame in the video industry) closest to the specified location. The keyframe is placed at an offset, in seconds, from the beginning of the stream.
  
  
  
  Video streams are usually encoded with two types of frames, keyframes (or I-frames) and P-frames. A keyframe contains an entire image, while a P-frame is an interim frame that provides additional video information between keyframes. A video stream typically has a keyframe every 10-50 frames.

  and so i need to understand how many p-frame and i-frame there are in a video encoded in .f4v format.

  i am on mac and on ubuntu, i don't care about the tool to use (mayebe some ffmpeg/mencoder call should be perfect), any advice ?