Archive for October, 2006

Some notes on Fraps

Sunday, October 29th, 2006

Here is what I currently know about Fraps v2 (v1 is supported by FFmpeg):

  • all data is stored in 32-bit little-endian words
  • first word indicates codec version and flag 0x8000000 – delta frame
  • second word is zero
  • next word is ‘FPSx’ magic
  • next three words are offsets in frame (from position 8) to packed YUV planes
  • each plane starts with 256 words – frequencies for each possible value
  • the rest of data¬† is bits packed in words
  • each bit looks like an input to state machine which outputs pair (value, skip) and changes its internal state
  • the rest is still needs to be figured out

Recent developments

Sunday, October 29th, 2006

Here is a quick list of what has been done recently:

  • LZW decoding in TIFF
  • 16-bit grayscale limited support (decoding PNG, read/write PGM and JPEG-LS but the latter is a bit buggy)
  • Some progress on Intel Music Codec decoder

Some progress

Sunday, October 15th, 2006

Ah, I still remember those days when FFmpeg got one new decoder once week or two.

Mike once mentioned here that one coder searches for ideas to implement. My situation is rather complimentary – I hardly manage to fullfill all requests from other people. Recently I’ve added two image decoders to FFmpeg – Targa (.tga) and TIFF. Both of them were done by request. The same situation was with Worms Video.

WavPack decoder was written by my own wish but there are already some people asking to write MPEG-4 ALS and Monkey’s Audio decoders. While the later is not possible to implement right now, I’ll implement both MP4 ALS decoder and encoder.