diff options
author | Mike Melanson <mike@multimedia.cx> | 2003-09-08 08:10:59 +0400 |
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committer | Mike Melanson <mike@multimedia.cx> | 2003-09-08 08:10:59 +0400 |
commit | 9937e686fe86cc463577208d67431dabe74ad2ae (patch) | |
tree | 3ca4b5537f199c8f6c62a0e722793eaaf7cea286 /libavcodec/dpcm.c | |
parent | 0a5f92a120118286961a28486cb2a1d96ca47627 (diff) |
New fringe codecs: WC3/Xan video, Xan DPCM, DK3 & DK4 ADPCM
Originally committed as revision 2217 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/dpcm.c')
-rw-r--r-- | libavcodec/dpcm.c | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/libavcodec/dpcm.c b/libavcodec/dpcm.c index bd3ad7fd0f..958e46467d 100644 --- a/libavcodec/dpcm.c +++ b/libavcodec/dpcm.c @@ -21,8 +21,17 @@ * @file: dpcm.c * Assorted DPCM (differential pulse code modulation) audio codecs * by Mike Melanson (melanson@pcisys.net) + * Xan DPCM decoder by Mario Brito (mbrito@student.dei.uc.pt) * for more information on the specific data formats, visit: * http://www.pcisys.net/~melanson/codecs/simpleaudio.html + * + * Note about using the Xan DPCM decoder: Xan DPCM is used in AVI files + * found in the Wing Commander IV computer game. These AVI files contain + * WAVEFORMAT headers which report the audio format as 0x01: raw PCM. + * Clearly incorrect. To detect Xan DPCM, you will probably have to + * special-case your AVI demuxer to use Xan DPCM if the file uses 'Xxan' + * (Xan video) for its video codec. Alternately, such AVI files also contain + * the fourcc 'Axan' in the 'auds' chunk of the AVI header. */ #include "avcodec.h" @@ -115,6 +124,9 @@ static int dpcm_decode_frame(AVCodecContext *avctx, int channel_number = 0; short *output_samples = data; int sequence_number; + int shift[2]; + unsigned char byte; + short diff; switch(avctx->codec->id) { @@ -171,6 +183,40 @@ static int dpcm_decode_frame(AVCodecContext *avctx, s->last_delta[i] = predictor[i]; break; + + case CODEC_ID_XAN_DPCM: + in = 0; + shift[0] = shift[1] = 4; + predictor[0] = LE_16(&buf[in]); + in += 2; + SE_16BIT(predictor[0]); + if (s->channels == 2) { + predictor[1] = LE_16(&buf[in]); + in += 2; + SE_16BIT(predictor[1]); + } + + while (in < buf_size) { + byte = buf[in++]; + diff = (byte & 0xFC) << 8; + if ((byte & 0x03) == 3) + shift[channel_number]++; + else + shift[channel_number] -= (2 * (byte & 3)); + /* saturate the shifter to a lower limit of 0 */ + if (shift[channel_number] < 0) + shift[channel_number] = 0; + + diff >>= shift[channel_number]; + predictor[channel_number] += diff; + + SATURATE_S16(predictor[channel_number]); + output_samples[out++] = predictor[channel_number]; + + /* toggle channel */ + channel_number ^= s->channels - 1; + } + break; } *data_size = out * sizeof(short); @@ -198,3 +244,14 @@ AVCodec interplay_dpcm_decoder = { NULL, dpcm_decode_frame, }; + +AVCodec xan_dpcm_decoder = { + "xan_dpcm", + CODEC_TYPE_AUDIO, + CODEC_ID_XAN_DPCM, + sizeof(DPCMContext), + dpcm_decode_init, + NULL, + NULL, + dpcm_decode_frame, +}; |