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lavc/avpacket: fill padding area on side data split. 

The padding data is assumed to be 0 in several places, notably in
subtitles. This problem was not detected with fate-sub-srt test because
the first element of the side data (x1) is 0 in the test, so the
trailing side data present in the packet wasn't read by the decoder. The
issue can be observed with a large enough x1.

It is also noted in FF_INPUT_BUFFER_PADDING_SIZE doxy that MPEG
bitstreams require that padding with 0, so it might fix other issues.
This commit is contained in:
Clément Bœsch 2013-06-01 14:07:24 +02:00
parent 9054e72529
commit 151b4947e5
1 changed files with 8 additions and 1 deletions
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9
libavcodec/avpacket.c
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@ -356,7 +356,7 @@ int av_packet_merge_side_data(AVPacket *pkt){
int av_packet_split_side_data(AVPacket *pkt){ int av_packet_split_side_data(AVPacket *pkt){
if (!pkt->side_data_elems && pkt->size >12 && AV_RB64(pkt->data + pkt->size - 8) == FF_MERGE_MARKER){ if (!pkt->side_data_elems && pkt->size >12 && AV_RB64(pkt->data + pkt->size - 8) == FF_MERGE_MARKER){
int i; int i;
unsigned int size; unsigned int size, orig_pktsize = pkt->size;
uint8_t *p; uint8_t *p;
p = pkt->data + pkt->size - 8 - 5; p = pkt->data + pkt->size - 8 - 5;
@ -389,6 +389,13 @@ int av_packet_split_side_data(AVPacket *pkt){
p-= size+5; p-= size+5;
} }
pkt->size -= 8; pkt->size -= 8;
/* FFMIN() prevents overflow in case the packet wasn't allocated with
* proper padding.
* If the side data is smaller than the buffer padding size, the
* remaining bytes should have already been filled with zeros by the
* original packet allocation anyway. */
memset(pkt->data + pkt->size, 0,
FFMIN(orig_pktsize - pkt->size, FF_INPUT_BUFFER_PADDING_SIZE));
pkt->side_data_elems = i+1; pkt->side_data_elems = i+1;
return 1; return 1;
} }