50 lines
1.9 KiB
Plaintext
50 lines
1.9 KiB
Plaintext
Technical notes:
|
|
---------------
|
|
|
|
Video:
|
|
-----
|
|
|
|
- The decision intra/predicted macroblock is the algorithm suggested
|
|
by the mpeg 1 specification.
|
|
|
|
- only Huffman based H263 is supported, mainly because of patent
|
|
issues.
|
|
|
|
- MPEG4 is supported, as an extension of the H263 encoder. MPEG4 DC
|
|
prediction is used, but not AC prediction. Specific VLC are used for
|
|
intra pictures. The output format is compatible with Open DIVX
|
|
version 47.
|
|
|
|
- MJPEG is supported, but in the current version the huffman tables
|
|
are not optimized. It could be interesting to add this feature for
|
|
the flash format.
|
|
|
|
- To increase speed, only motion vectors (0,0) are tested for real
|
|
time compression. NEW: now motion compensation is done with several
|
|
methods : none, full, log, and phods. The code is mmx/sse optimized.
|
|
|
|
- In high quality mode, full search is used for motion
|
|
vectors. Currently, only fcode = 1 is used for both H263/MPEG1. Half
|
|
pel vectors are used.
|
|
|
|
Audio:
|
|
-----
|
|
|
|
- The mpeg audio layer 2 compatible encoder was rewritten from
|
|
scratch. It is one of the simplest encoder you can imagine (800
|
|
lines of C code !). It is also one of the fastest because of its
|
|
simplicity. There are still some problems of overflow. A minimal
|
|
psycho acoustic model could be added. Currently, stereo is
|
|
supported, but not joint stereo.
|
|
|
|
- The AC3 audio encoder was rewritten from scratch. It is fairly
|
|
naive, but the result are quiet interesting at 64 kbit/s. It
|
|
includes extensions for low sampling rates used in some Internet
|
|
formats. Differential and coupled stereo is not handled. Stereo
|
|
channels are simply handled as two mono channels.
|
|
|
|
- The mpeg audio layer 3 decoder was rewritten from scratch. It uses
|
|
only integers and can be 16 bit precision for the synthesis filter
|
|
at the expense of a slight precision loss. A slower bit exact mode
|
|
is available too for compliance testing.
|