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• avformat/oggenc : Avoid allocating and copying when writing page data

  3 mai 2020, par Andreas Rheinhardt

  avformat/oggenc : Avoid allocating and copying when writing page data
  When the Ogg muxer writes a page, it has to do three things : It needs to
  
  write a page header, then it has to actually copy the page data and then
  
  it has to calculate and write a CRC checksum of both header as well as
  
  data at a certain position in the page header.
  To do this, the muxer used a dynamic buffer for both writing as well as
  
  calculating the checksum via an AVIOContext's feature to automatically
  
  calculate checksums on the data it writes. This entails an allocation of
  
  an AVIOContext, of the opaque specific to dynamic buffers and of the
  
  buffer itself (which may be reallocated multiple times) as well as
  
  memcopying the data (first into the AVIOContext's small write buffer,
  
  then into the dynamic buffer's big buffer).
  This commit changes this : The page header is no longer written into a
  
  dynamic buffer any more ; instead the (small) page header is written into
  
  a small buffer on the stack. The CRC is then calculated directly via
  
  av_crc() on both the page header as well as the page data. Then both the
  
  page header and the page data are written.
  Finally, ogg_write_page() can now no longer fail, so it has been
  
  modified to return nothing ; this also fixed a bug in the only caller of
  
  this function : It didn't check the return value.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/oggenc.c

• ffprobe : allow side-data selection by element

  31 janvier 2022, par Gyan Doshi

  ffprobe : allow side-data selection by element
  At present, side data printing forces display for all levels i.e.
  
  stream, packets and frames. This can bloat output and also force
  
  decode of all frames in selected streams.
  Now, stream_side_data[=type], packet_side_data[=type] &
  
  frame_side_data[=type] can be used with -show_entries to specify carrier
  
  element.
  

  • [DH] fftools/ffprobe.c

• Media Source Extensions - Identifying when there is no more data

  8 octobre 2015, par galbarm

  I’m creating a fragmented MP4 of a real-time live content with constant 10FPS but occasionally a frame gets dropped before being feed to the MP4 creation process.
  The MP4 is transmitted to the web through a web socket.

  Due to the occasional frames drop, the playback speed of the file is effectively slightly greater than 1x, because the player plays at 10FPS.
  Since this is a live content, after some duration, the player reaches the present time and has no data to play.

  Now, to the MSE issue :
  What seems to happen in Chrome, when the player doesn’t have enough data to continue playing, is that it pauses for 1-2 secs, then plays it very fast, and vice versa. So at this point the user experience becomes very bad.
  The issue was discussed here :
  https://www.w3.org/Bugs/Public/show_bug.cgi?id=28379

  My idea to workaround this, is to identify the state (having no more data), change playback rate to 0.9 for a few seconds to allow some buffering, and then switch back to 1.0.
  The problem is that I couldn’t find a way to identify the state.
  The readystate of the media element seems to always have the value of "HAVE_ENOUGH_DATA" even when the issue starts.

  Does the MSE API exposes a way identify the state that I have described ?