[Ffmpeg-devel] [PATCH] flacenc - lpc and options

[Justin Ruggles]

Hello,

Another FLAC encoder patch is done.  This adds LPC encoding.  Right now
there is only 1 order search method, which does a quick estimate based
on the reflection coefficients.

I also added compression options which can be changed by setting them in
the AVCodecContext or by using AVOption.  Here is the solution I decided on:

1) added 'compression_level' to AVCodecContext.  it is set to
FF_COMPRESSION_DEFAULT (-1) by default.  this could be easily reused in
other codecs (e.g. PNG, ZLIB).

2) added 8 compression options to AVCodecContext which are used by the
encoder.  most of them are set to -1 by default, which indicates for the
encoder to use its default setting.  this is so that other codecs can
reuse these fields if they wish, and can have different default values.

3) modified flacenc.c to first check for the compression_level and set
all the options based on that value, then read the other AVCodecContext
values and override the defaults if they are explicitly set by the user.

If any of this should be changed, let me know.  Michael's idea of a
'preset' field in AVCodecContext would work, but it was unnecessary in
this case.  I guess it could still be added for shortcuts like "best" or
"fast".

Since I have not yet added any more extensive order search options, the
compression level only goes from 0 to 5 for now.  Below are the results
of a few tests comparing ffmpeg to the reference encoder.  The faster
decode times for the ffmpeg-generated files are mostly due to the fact
that MD5 sums are not implemented yet, so the decoder doesn't do any
verification.

On that note, when I do add MD5 support, could I put the MD5-specific
code in its own files (libavutil/md5.c, md5.h)?  It could possibly be
reused in the regression tests by adding an md5 test format to libavformat.

-Justin


=======================================================
Hongroise.wav
playing time: 30.00s
original audio size: 5292100

flac:

level   enc time    bytes    ratio   kbps    dec time
-----  ---------  --------   -----  ------  ---------
  0        2.80s   2373649   0.448   632.9      1.08s
  1        3.05s   2371546   0.448   632.4      1.07s
  2        3.77s   2363295   0.446   630.2      1.10s
  3        4.24s   2040056   0.385   544.0      1.35s
  4        5.12s   2052680   0.387   547.3      1.40s
  5        6.50s   2035756   0.384   542.8      1.45s

ffmpeg:

level   enc time    bytes    ratio   kbps    dec time
-----  ---------  --------   -----  ------  ---------
  0        2.20s   2374305   0.448   633.1      0.87s
  1        3.03s   2372543   0.448   632.6      0.89s
  2        3.31s   2368870   0.447   631.6      0.91s
  3        4.12s   1990216   0.376   530.7      1.08s
  4        4.55s   1952459   0.368   520.6      1.13s
  5        4.82s   1951425   0.368   520.3      1.13s
=======================================================


=======================================================
compilation.wav
playing time: 65.23s
original audio size: 11505908

flac:

level   enc time    bytes    ratio   kbps    dec time
-----  ---------  --------   -----  ------  ---------
  0        6.53s   6398288   0.556   784.7      2.56s
  1        6.94s   6279772   0.545   770.1      2.62s
  2        8.56s   6241038   0.542   765.4      2.56s
  3        9.17s   6132773   0.533   752.1      3.04s
  4       11.25s   6013517   0.522   737.5      3.36s
  5       14.35s   5996495   0.521   735.4      3.26s

ffmpeg:

level   enc time    bytes    ratio   kbps    dec time
-----  ---------  --------   -----  ------  ---------
  0        5.08s   6294599   0.547   771.9      2.04s
  1        6.36s   6256409   0.543   767.3      2.11s
  2        6.74s   6243269   0.542   765.6      1.97s
  3        8.90s   5968820   0.518   732.0      2.69s
  4        9.84s   5956367   0.517   730.5      2.74s
  5       10.43s   5940655   0.516   728.5      2.79s
=======================================================


=======================================================
songs_of_love.wav
playing time: 270.55s
original audio size: 47724432

flac:

level   enc time    bytes    ratio   kbps    dec time
-----  ---------  --------   -----  ------  ---------
  0       27.17s  27316733   0.572   807.7     10.64s
  1       28.64s  26237781   0.549   775.8     10.88s
  2       35.87s  26170357   0.548   773.8     10.73s
  3       38.80s  26259292   0.550   776.4     13.23s
  4       47.62s  25299173   0.530   748.0     13.97s
  5       60.32s  25258739   0.529   746.8     13.92s

ffmpeg:

level   enc time    bytes    ratio   kbps    dec time
-----  ---------  --------   -----  ------  ---------
  0       19.60s  26353714   0.552   779.2      8.72s
  1       26.10s  26223349   0.549   775.4      8.53s
  2       27.05s  26194053   0.548   774.5      8.61s
  3       37.25s  25018815   0.524   739.7     11.25s
  4       40.54s  24977928   0.523   738.5     11.33s
  5       42.40s  24971002   0.523   738.3     11.13s
=======================================================
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