[FFmpeg-devel] [PATCH] latmenc: Check for LOAS sync word

[James Almer]

On Fri, Jan 11, 2013 at 4:57 PM, Paul B Mahol <onemda at gmail.com> wrote:
>
> On 1/11/13, James Almer <jamrial at gmail.com> wrote:
> > On 08/01/13 3:14 PM, James Almer wrote:
> >> Write the packet unaltered if found.
> >>
> >> Fixes ticket #1917
> >>
> >> Signed-off-by: James Almer <jamrial at gmail.com>
> >> ---
> >>  libavformat/latmenc.c |    2 +-
> >>  1 files changed, 1 insertions(+), 1 deletions(-)
> >>
> >> diff --git a/libavformat/latmenc.c b/libavformat/latmenc.c
> >> index 233eab8..b882382 100644
> >> --- a/libavformat/latmenc.c
> >> +++ b/libavformat/latmenc.c
> >> @@ -149,7 +149,7 @@ static int latm_write_packet(AVFormatContext *s,
> >> AVPacket *pkt)
> >>      int i, len;
> >>      uint8_t loas_header[] = "\x56\xe0\x00";
> >>
> >> -    if (s->streams[0]->codec->codec_id == AV_CODEC_ID_AAC_LATM)
> >> +    if (pkt->size > 2 && pkt->data[0] == 0x56 && (pkt->data[1] >> 4) ==
> >> 0xe)
> >>          return ff_raw_write_packet(s, pkt);
> >>
> >>      if (pkt->size > 2 && pkt->data[0] == 0xff && (pkt->data[1] >> 4) ==
> >> 0xf) {
>
> Shouldn't  you check exact header and not just part of it?
>
> How possible is that valid packet than need header will have first 3 bytes same
> as loas header?

As Kunhya said, that's the extent of the header.

I added a check to compare the size of the packet with the size
reported at the end
of the LOAS header (last 13 bits).
That should make sure only actual LOAS packets pass the entire set of checks.

Regards.
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