18 Sept 2021, 12:03 by pr...@xvid.org:
> ---
> libavcodec/siren.c | 32 +++++++++++++++++++++++++++++++-
> 1 file changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/siren.c b/libavcodec/siren.c
> index 92fd3632f5..2d3969f24c 100644
> --- a/libavcodec/siren.c
> +++ b/libavcodec/siren.c
> @@ -756,7 +756,37 @@ 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;
> + }
> + }
>
Looks good to me.
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