James Almer: > On 5/31/2020 4:11 PM, Andreas Rheinhardt wrote: >> James Almer: >>> On 5/31/2020 2:58 PM, Andreas Rheinhardt wrote:>> (Anyway, when this >>> function is switched to size_t, >>>> the correct error would be AVERROR(ERANGE). It is actually already the >>>> correct error in case size > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE.) >>>> 3. That's unfortunately only a tiny fraction of the work to do before >>>> this switch can happen: >>>> a) libavcodec/mjpega_dump_header_bsf.c contains the following line: >>>> for (i = 0; i < in->size - 1; i++) { >>>> If in->size == 0, then this will not have the desired effect, because >>>> the subtraction now wraps around. There are probably more places like >>>> this (and overflow checks that don't work as expected any more). We >>>> would need to find them all and port them. >>> >>> Empty packets are considered flush packets, right? Guess we should be >>> rejecting packets where pkt->size == 0 && pkt->data != NULL in >>> av_bsf_send_packet(), same as we do in avcodec_send_packet(). I'll send >>> a patch for that later. >>> >> The only way one can signal flushing to a bsf is by using av_bsf_flush. >> Empty packets (data == NULL and no side_data) are considered eof. > > Yes, that's what i meant. The entire codebase uses flush, drain and EOF > interchangeably in some cases. > >> Packets with data != NULL, size = 0 and no side data are currently >> considered normal packets (a possible use-case would be to send some >> timestamps to the bsf, although no bsf currently makes use of this; but >> who knows what needs a future bsf has). > > data != NULL && size == 0 should IMO not be accepted. If we want to > signal that we're feeding the bsf something like timestamps only, we'd > have to find a different way to do it than setting pkt->data to some > bogus value that's not NULL in order to bypass the IS_EMPTY() check. > Bogus value? You seem to believe that pkt->data just points to somewhere in memory; in a valid packet it points to a buffer of size pkt->size + AV_INPUT_BUFFER_PADDING_SIZE (even when pkt->size == 0). av_packet_make_refcounted creates such packets if the input packet doesn't have data (and the h264_mp4toannexb bsf currently relies on this).
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