On 17/03/16 14:11, Mark Thompson wrote:
> 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 <m...@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.
Something like this, perhaps (not thoroughly tested).
>From 439408a7f25b1dc5146a580fec487ad0b2c0163a Mon Sep 17 00:00:00 2001
From: Mark Thompson <m...@jkqxz.net>
Date: Thu, 17 Mar 2016 13:41:02 +0000
Subject: [PATCH] lavc/hevc: Log warnings for garbage found when parsing
bytestream.
---
libavcodec/hevc_parse.c | 43 +++++++++++++++++++++++++++++++++++++++----
1 file changed, 39 insertions(+), 4 deletions(-)
diff --git a/libavcodec/hevc_parse.c b/libavcodec/hevc_parse.c
index 63ed84a..a153747 100644
--- a/libavcodec/hevc_parse.c
+++ b/libavcodec/hevc_parse.c
@@ -227,13 +227,48 @@ int ff_hevc_split_packet(HEVCContext *s, HEVCPacket *pkt, const uint8_t *buf, in
return AVERROR_INVALIDDATA;
}
} else {
- /* search start code */
- while (buf[0] != 0 || buf[1] != 0 || buf[2] != 1) {
+ int i;
+ // Skip leading zeroes before the start code in the bytestream (or,
+ // equivalently, trailing zeroes of the previous NAL unit).
+ while (buf[0] == 0 && buf[1] == 0 && buf[2] == 0) {
++buf;
--length;
- if (length < 4) {
- av_log(avctx, AV_LOG_ERROR, "No start code is found.\n");
+ if (length < 4)
+ break;
+ }
+ if (length < 4) {
+ if (pkt->nb_nals == 0) {
+ av_log(avctx, AV_LOG_ERROR, "No start code found: packet "
+ "contains only zero bytes.\n");
return AVERROR_INVALIDDATA;
+ } else {
+ // There was a NAL unit with trailing zeroes which we
+ // are ignoring.
+ break;
+ }
+ }
+ // We should find a start code immediately, if we don't then there
+ // is something funny going on in the packet.
+ for (i = 0; buf[0] != 0 || buf[1] != 0 || buf[2] != 1; i++) {
+ ++buf;
+ --length;
+ if (length < 4)
+ break;
+ }
+ if (i > 0) {
+ if (length < 4) {
+ if (pkt->nb_nals > 0) {
+ av_log(avctx, AV_LOG_WARNING, "Skipped %d bytes of "
+ "garbage at end of packet.\n", i);
+ break;
+ } else {
+ av_log(avctx, AV_LOG_ERROR, "No start code found: "
+ "packet contains garbage.\n");
+ return AVERROR_INVALIDDATA;
+ }
+ } else {
+ av_log(avctx, AV_LOG_WARNING, "Skipped %d bytes of "
+ "garbage before finding a start code.\n", i);
}
}
--
2.7.0
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