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avcodec/siren: add checksum calculation 

Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Peter Ross <pross@xvid.org>
This commit is contained in:
Peter Ross 2021-09-04 21:14:37 +10:00
parent e40593c050
commit 855014ff83
1 changed files with 31 additions and 1 deletions
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32
libavcodec/siren.c
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@ -760,7 +760,37 @@ static int siren_decode(AVCodecContext *avctx, void *data,
frame_error = 1;
}
skip_bits(gb, s->checksum_bits);
if ((avctx->err_recognition & AV_EF_CRCCHECK) && s->checksum_bits) {
static const uint16_t ChecksumTable[4] = {0x7F80, 0x7878, 0x6666, 0x5555};
int wpf, checksum, sum, calculated_checksum, temp1;
checksum = get_bits(gb, s->checksum_bits);
wpf = bits_per_frame / 16;
sum = 0;
for (int i = 0; i < wpf - 1; i++)
sum ^= AV_RB16(avpkt->data + i * 2) << (i % 15);
sum ^= (AV_RB16(avpkt->data + (wpf - 1) * 2) & ~checksum) << ((wpf - 1) % 15);
sum = (sum >> 15) ^ (sum & 0x7FFF);
calculated_checksum = 0;
for (int i = 0; i < 4; i++) {
temp1 = ChecksumTable[i] & sum;
for (int j = 8; j > 0; j >>= 1)
temp1 ^= temp1 >> j;
calculated_checksum <<= 1;
calculated_checksum |= temp1 & 1;
}
if (checksum != calculated_checksum) {
av_log(avctx, AV_LOG_WARNING, "Invalid checksum\n");
if (avctx->err_recognition & AV_EF_EXPLODE)
return AVERROR_INVALIDDATA;
frame_error = 1;
}
}
if (frame_error) {
memcpy(s->imdct_in, s->backup_frame, number_of_valid_coefs * sizeof(float));