[FFmpeg-devel] [PATCH] lavc/hevc: Allow arbitrarily many trailing_zero_8bits after a NAL unit in bytestream format.

[Mark Thompson]

On 17/03/16 13:57, Michael Niedermayer wrote:
> On Thu, Mar 17, 2016 at 01:48:37PM +0000, Mark Thompson wrote:
>>  hevc_parse.c |   10 ++++++++--
>>  1 file changed, 8 insertions(+), 2 deletions(-)
>> daf73b16f8185221a1e8112ab1928157a855fe76  0001-lavc-hevc-Allow-arbitrary-garbage-in-bytestream-as-l.patch
>> From 725fb99402fa468e5f11f94e0ec09b2e0c91e6b2 Mon Sep 17 00:00:00 2001
>> From: Mark Thompson <mrt at jkqxz.net>
>> Date: Thu, 17 Mar 2016 13:41:02 +0000
>> Subject: [PATCH] lavc/hevc: Allow arbitrary garbage in bytestream as long as
>>  at least one NAL unit is found.
>>
>> ---
>>  libavcodec/hevc_parse.c | 10 ++++++++--
>>  1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavcodec/hevc_parse.c b/libavcodec/hevc_parse.c
>> index 63ed84a..d557cc7 100644
>> --- a/libavcodec/hevc_parse.c
>> +++ b/libavcodec/hevc_parse.c
>> @@ -232,8 +232,14 @@ int ff_hevc_split_packet(HEVCContext *s, HEVCPacket *pkt, const uint8_t *buf, in
>>                  ++buf;
>>                  --length;
>>                  if (length < 4) {
>> -                    av_log(avctx, AV_LOG_ERROR, "No start code is found.\n");
>> -                    return AVERROR_INVALIDDATA;
>> +                    if (pkt->nb_nals > 0) {
>> +                        // No more start codes: we discarded some irrelevant
>> +                        // bytes at the end of the packet.
>> +                        return 0;
> 
> does the case of garbage still print something at some level?
> if not, it should. It could be usefull for debuging to know if theres
> something funky going on with NAL parsing

It already doesn't print anything for the garbage it accepts between NAL units
in a packet; this change just makes it consistent by silently accepting garbage
at the end as well.  If we want to log something for all of these cases then it
would have to look more like the first version of the patch to skip zeroes and
then log a warning if the second search does not find a start code immediately.

- Mark