[FFmpeg-devel] [PATCH] adpcm-ima-wav header and codec

Timofei tim
Mon Oct 15 17:55:29 CEST 2007


Hi.

I found a few bugs in the adpcm-ima codec.
This format is used in smv video by sigmatel-based mp3 players.

1) The field 'bytes-per-second' in WAV header is set incorrectly.
This breaks seeking on hardware player.
I found the bitrate value used in calculations comes from commandline 
and does not reflect reality.
The adpcm-bitrate.patch puts correct bitrate in avctx.
This fixes wav header, but the ffmpeg program still prints wrong bitrate
during encoding.

2) adpcm-codec.patch
In adpcm_encode_frame() predictor for right channel gets initialized by 
2nd sample of the left channel instead of 1st sample of the right channel.

The adpcm_decode_frame() loses first sample in block.
This sample initializes predictor and then gets lost instead of being 
copied to output.

3) adpcm-index_step.patch - initialization of index_step added.
This patch depends on adpcm-codec.patch

4) adpcm-guard.patch - not a bug. Just removed unnecessary guarding 
&=0x0f around adpcm_ima_compress_sample().

Regards.
	Tim.
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