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screenpresso: Correctly handle keyframes 

The first byte contains compression level together with keyframe status.
When a frame is not interpreted correctly, its data is summed to the
reference, and would degrade over time, producing an incorrect result.

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
This commit is contained in:
Vittorio Giovara 2016-03-29 20:30:48 +02:00
parent 95db8c757c
commit ec8a69fab6
1 changed files with 3 additions and 4 deletions
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7
libavcodec/screenpresso.c
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@ -115,10 +115,9 @@ static int screenpresso_decode_frame(AVCodecContext *avctx, void *data,
return AVERROR_INVALIDDATA;
}
/* Basic sanity check, but not really harmful */
if (avpkt->data[0] != 0x73 && avpkt->data[0] != 0x72)
av_log(avctx, AV_LOG_WARNING, "Unknown header 0x%02X\n", avpkt->data[0]);
keyframe = (avpkt->data[0] == 0x73);
/* Compression level (4 bits) and keyframe information (1 bit) */
av_log(avctx, AV_LOG_DEBUG, "Compression level %d\n", avpkt->data[0] >> 4);
keyframe = avpkt->data[0] & 1;
/* Pixel size */
component_size = ((avpkt->data[1] >> 2) & 0x03) + 1;