int ff_flac_decode_frame_header(AVCodecContext *avctx, GetBitContext *gb, FLACFrameInfo *fi) { int bs_code, sr_code, bps_code; /* frame sync code */ 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 */ 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(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(avctx, AV_LOG_ERROR, "invalid sample size code (%d)\n", bps_code); return -1; } fi->bps = sample_size_table[bps_code]; /* reserved bit */ if (get_bits1(gb)) { av_log(avctx, AV_LOG_ERROR, "broken stream, invalid padding\n"); return -1; } /* sample or frame count */ if (get_utf8(gb) < 0) { av_log(avctx, AV_LOG_ERROR, "utf8 fscked\n"); return -1; } /* blocksize */ if (bs_code == 0) { av_log(avctx, AV_LOG_ERROR, "reserved blocksize code: 0\n"); return -1; } else if (bs_code == 6) { fi->blocksize = get_bits(gb, 8) + 1; } else if (bs_code == 7) { fi->blocksize = get_bits(gb, 16) + 1; } else { fi->blocksize = ff_flac_blocksize_table[bs_code]; } /* sample rate */ if (sr_code < 12) { fi->samplerate = ff_flac_sample_rate_table[sr_code]; } else if (sr_code == 12) { fi->samplerate = get_bits(gb, 8) * 1000; } else if (sr_code == 13) { fi->samplerate = get_bits(gb, 16); } else if (sr_code == 14) { fi->samplerate = get_bits(gb, 16) * 10; } else { av_log(avctx, AV_LOG_ERROR, "illegal sample rate code %d\n", sr_code); return -1; } /* header CRC-8 check */ 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(avctx, AV_LOG_ERROR, "header crc mismatch\n"); return -1; } return 0; }