[FFmpeg-devel] [PATCH] avformat: remove request_probe assert from ff_read_packet

[Andreas Cadhalpun]

On 18.10.2016 22:56, Michael Niedermayer wrote:
> On Tue, Oct 18, 2016 at 10:31:37PM +0200, Andreas Cadhalpun wrote:
>> Nothing guarantees to set request_probe to -1, so this assert can be
>> triggered, e.g. if st->probe_packets is 0.
> 
> probe_codec() called with NULL should cause
> st->probe_packets = 0
> st->request_probe = -1;

Yes, but request_probe can be change to a different value later on,
e.g. in ff_parse_mpeg2_descriptor:

int ff_read_packet(AVFormatContext *s, AVPacket *pkt)
{
[...]
            if (s->internal->raw_packet_buffer_remaining_size <= 0)
                if ((err = probe_codec(s, st, NULL)) < 0) // probe_packets = 0, request_probe = -1
                    return err;
[...]
        ret = s->iformat->read_packet(s, pkt);
~~~
ff_parse_mpeg2_descriptor([...])
{
[...]
    switch (desc_tag) {
[...]
    case 0x05: /* registration descriptor */
[...]
                st->request_probe = 50;
[...]
}
~~~
[...]
                if (st->probe_packets) // still 0
                    if ((err = probe_codec(s, st, NULL)) < 0)
                        return err;
                av_assert0(st->request_probe <= 0); // now 50
SIGABRT

Best regards,
Andreas