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• How to convert from AV_PIX_FMT_BGRA to PIX_FMT_PAL8 ?

  29 juillet 2014, par Jona

  I’m having a hard time converting my images from AV_PIX_FMT_BGRA to PIX_FMT_PAL8. Unfortunately sws_getCachedContext doesn’t support the conversion to PIX_FMT_PAL8.

  What I’m trying to do is convert my images into a GIF video with higher quality output. It seems that PIX_FMT_PAL8 could potentially provide the higher quality output I’m looking for.

  According to this documentation I need to palettize the pixel data, but I have no clue how to do that.

  When the pixel format is palettized RGB (PIX_FMT_PAL8), the palettized
  image data is stored in AVFrame.data[0]. The palette is transported in
  AVFrame.data[1], is 1024 bytes long (256 4-byte entries) and is
  formatted the same as in PIX_FMT_RGB32 described above (i.e., it is
  also endian-specific). Note also that the individual RGB palette
  components stored in AVFrame.data[1] should be in the range 0..255.
  This is important as many custom PAL8 video codecs that were designed
  to run on the IBM VGA graphics adapter use 6-bit palette components.

  Any help or direction would be appreciated.

• How do the ffmpeg SAP and SDP demuxer interact actually ?

  13 mars 2015, par πάντα ῥεῖ

  I’m about creating a simple (demon) application using the libav*(libavformat) API that is supposed to capture the SAP announcements, and cache the according SDP records payload information into a file based services record list.

  I’m pretty new to ffmpeg, and don’t quite understand how the SAP and SDP demuxer actually interact.

  All of the uses and examples I could find in the ffmpeg environment, are about the standard behavior, that ffmpeg services just try to open the first associated AV stream, as described in the received announcements. But I don’t need to open the AV stream announced with the SDP record, but just to parse the information and add/remove it to/from my cached list of available AV streams.

  I have a (VLC) MiniSAP server running, that broadcasts the SAP/SDP packets in my network. Using the

  AVFormatContext *s = NULL;
  
  int ret = avformat_open_input(&s, "sap://", NULL, NULL);
  
  if (ret < 0)
  
      abort();

  works so far for me, as long I have the MiniSAP server running.

  I just don’t have any clue, how to get an AVFormatContext* for the SDP demuxer in the next step and decode the payload info. I’d be happy even using a decoding callback, since the SDP payload is a pretty simple section/key value pair text format anyway.

  Can anyone point me into the right direction, what to do ?

• ffmpeg hls stream hangs after a few seconds

  21 janvier 2017, par pluralism

  I’m studying the FFMPEG tool, although I’m having some difficulties while forwarding an HLS stream. I’m executing the command ffmpeg -i http://example.com/hls/index.m3u8 -c copy /path/to/web/dir/index.m3u8 in order to create a m3u8 playlist which in turn will create all the TS files every 2 seconds(default). I’m also running ffplay -i index.m3u8 on another window, although the video hangs after 2 or 3 seconds. Here it is the content of my m3u8 playlist :

  #EXTM3U
  
  #EXT-X-VERSION:3
  
  #EXT-X-TARGETDURATION:2
  
  #EXT-X-MEDIA-SEQUENCE:105
  
  #EXTINF:2.000000,
  
  index105.ts
  
  #EXTINF:2.000000,
  
  index106.ts
  
  #EXTINF:2.000000,
  
  index107.ts
  
  #EXTINF:2.000000,
  
  index108.ts
  
  #EXTINF:1.960000,
  
  index109.ts

  How could I solve this problem ? Thanks in advance.