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flacdec: split frame header decoding and validation into a separate 

function

Originally committed as revision 18175 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2009-03-24 01:17:55 +00:00
parent 77544e5b91
commit cd98a03024
2 changed files with 68 additions and 40 deletions
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15
libavcodec/flac.h
View File

@ -57,22 +57,31 @@ enum FLACExtradataFormat {
FLAC_EXTRADATA_FORMAT_FULL_HEADER = 1
};
#define FLACCOMMONINFO \
int samplerate; /**< sample rate */\
int channels; /**< number of channels */\
int bps; /**< bits-per-sample */\
/**
* Data needed from the Streaminfo header for use by the raw FLAC demuxer
* and/or the FLAC decoder.
*/
#define FLACSTREAMINFO \
FLACCOMMONINFO \
int max_blocksize; /**< maximum block size, in samples */\
int max_framesize; /**< maximum frame size, in bytes */\
int samplerate; /**< sample rate */\
int channels; /**< number of channels */\
int bps; /**< bits-per-sample */\
int64_t samples; /**< total number of samples */\
typedef struct FLACStreaminfo {
FLACSTREAMINFO
} FLACStreaminfo;
typedef struct FLACFrameInfo {
FLACCOMMONINFO
int blocksize; /**< block size of the frame */
int ch_mode; /**< channel decorrelation mode */
} FLACFrameInfo;
/**
* Parse the Streaminfo metadata block
* @param[out] avctx codec context to set basic stream parameters

93
libavcodec/flacdec.c
View File

@ -480,75 +480,80 @@ static inline int decode_subframe(FLACContext *s, int channel)
return 0;
}
static int decode_frame(FLACContext *s)
/**
* Validate and decode a frame header.
* @param avctx AVCodecContext to use as av_log() context
* @param gb GetBitContext from which to read frame header
* @param[out] fi frame information
*/
static int decode_frame_header(AVCodecContext *avctx, GetBitContext *gb,
FLACFrameInfo *fi)
{
int bs_code, sr_code, bps_code, i;
int ch_mode, bps, blocksize, samplerate, channels;
GetBitContext *gb = &s->gb;
int bs_code, sr_code, bps_code;
/* frame sync code */
skip_bits(&s->gb, 16);
skip_bits(gb, 16);
/* block size and sample rate codes */
bs_code = get_bits(gb, 4);
sr_code = get_bits(gb, 4);
/* channels and decorrelation */
ch_mode = get_bits(gb, 4);
if (ch_mode < FLAC_MAX_CHANNELS) {
channels = ch_mode + 1;
ch_mode = FLAC_CHMODE_INDEPENDENT;
} else if (ch_mode <= FLAC_CHMODE_MID_SIDE) {
channels = 2;
fi->ch_mode = get_bits(gb, 4);
if (fi->ch_mode < FLAC_MAX_CHANNELS) {
fi->channels = fi->ch_mode + 1;
fi->ch_mode = FLAC_CHMODE_INDEPENDENT;
} else if (fi->ch_mode <= FLAC_CHMODE_MID_SIDE) {
fi->channels = 2;
} else {
av_log(s->avctx, AV_LOG_ERROR, "invalid channel mode: %d\n", ch_mode);
av_log(avctx, AV_LOG_ERROR, "invalid channel mode: %d\n", fi->ch_mode);
return -1;
}
/* bits per sample */
bps_code = get_bits(gb, 3);
if (bps_code == 3 || bps_code == 7) {
av_log(s->avctx, AV_LOG_ERROR, "invalid sample size code (%d)\n",
av_log(avctx, AV_LOG_ERROR, "invalid sample size code (%d)\n",
bps_code);
return -1;
}
bps = sample_size_table[bps_code];
fi->bps = sample_size_table[bps_code];
/* reserved bit */
if (get_bits1(gb)) {
av_log(s->avctx, AV_LOG_ERROR, "broken stream, invalid padding\n");
av_log(avctx, AV_LOG_ERROR, "broken stream, invalid padding\n");
return -1;
}
/* sample or frame count */
if (get_utf8(gb) < 0) {
av_log(s->avctx, AV_LOG_ERROR, "utf8 fscked\n");
av_log(avctx, AV_LOG_ERROR, "utf8 fscked\n");
return -1;
}
/* blocksize */
if (bs_code == 0) {
av_log(s->avctx, AV_LOG_ERROR, "reserved blocksize code: 0\n");
av_log(avctx, AV_LOG_ERROR, "reserved blocksize code: 0\n");
return -1;
} else if (bs_code == 6) {
blocksize = get_bits(gb, 8) + 1;
fi->blocksize = get_bits(gb, 8) + 1;
} else if (bs_code == 7) {
blocksize = get_bits(gb, 16) + 1;
fi->blocksize = get_bits(gb, 16) + 1;
} else {
blocksize = ff_flac_blocksize_table[bs_code];
fi->blocksize = ff_flac_blocksize_table[bs_code];
}
/* sample rate */
if (sr_code < 12) {
samplerate = ff_flac_sample_rate_table[sr_code];
fi->samplerate = ff_flac_sample_rate_table[sr_code];
} else if (sr_code == 12) {
samplerate = get_bits(gb, 8) * 1000;
fi->samplerate = get_bits(gb, 8) * 1000;
} else if (sr_code == 13) {
samplerate = get_bits(gb, 16);
fi->samplerate = get_bits(gb, 16);
} else if (sr_code == 14) {
samplerate = get_bits(gb, 16) * 10;
fi->samplerate = get_bits(gb, 16) * 10;
} else {
av_log(s->avctx, AV_LOG_ERROR, "illegal sample rate code %d\n",
av_log(avctx, AV_LOG_ERROR, "illegal sample rate code %d\n",
sr_code);
return -1;
}
@ -557,18 +562,32 @@ static int decode_frame(FLACContext *s)
skip_bits(gb, 8);
if (av_crc(av_crc_get_table(AV_CRC_8_ATM), 0, gb->buffer,
get_bits_count(gb)/8)) {
av_log(s->avctx, AV_LOG_ERROR, "header crc mismatch\n");
av_log(avctx, AV_LOG_ERROR, "header crc mismatch\n");
return -1;
}
if (channels != s->channels) {
return 0;
}
static int decode_frame(FLACContext *s)
{
int i;
GetBitContext *gb = &s->gb;
FLACFrameInfo fi;
if (decode_frame_header(s->avctx, gb, &fi)) {
av_log(s->avctx, AV_LOG_ERROR, "invalid frame header\n");
return -1;
}
if (fi.channels != s->channels) {
av_log(s->avctx, AV_LOG_ERROR, "switching channel layout mid-stream "
"is not supported\n");
return -1;
}
s->ch_mode = ch_mode;
s->ch_mode = fi.ch_mode;
if (bps && bps != s->bps) {
if (fi.bps && fi.bps != s->bps) {
av_log(s->avctx, AV_LOG_ERROR, "switching bps mid-stream is not "
"supported\n");
return -1;
@ -583,20 +602,20 @@ static int decode_frame(FLACContext *s)
s->is32 = 0;
}
if (blocksize > s->max_blocksize) {
av_log(s->avctx, AV_LOG_ERROR, "blocksize %d > %d\n", blocksize,
if (fi.blocksize > s->max_blocksize) {
av_log(s->avctx, AV_LOG_ERROR, "blocksize %d > %d\n", fi.blocksize,
s->max_blocksize);
return -1;
}
s->blocksize = blocksize;
s->blocksize = fi.blocksize;
if (samplerate == 0) {
samplerate = s->samplerate;
} else if (samplerate != s->samplerate) {
if (fi.samplerate == 0) {
fi.samplerate = s->samplerate;
} else if (fi.samplerate != s->samplerate) {
av_log(s->avctx, AV_LOG_WARNING, "sample rate changed from %d to %d\n",
s->samplerate, samplerate);
s->samplerate, fi.samplerate);
}
s->samplerate = s->avctx->sample_rate = samplerate;
s->samplerate = s->avctx->sample_rate = fi.samplerate;
// dump_headers(s->avctx, (FLACStreaminfo *)s);