Bug#789254: This sample seems not to be processable by FFmpeg

[Peter Belkner]

On 22.06.2015 10:09, Carl Eugen Hoyos wrote:
> Hi!
>
> On Mon, 22 Jun 2015, Peter Belkner wrote:
>
>>     if (0!=*got_packet) {
>> av_packet_rescale_ts(pkt,cc->time_base,st->time_base);
>> +     // where do the "magic" factor 0.5 come from?
>> +     pkt->dts>>=1;
>> +     pkt->pts>>=1;
>> +     pkt->duration>>=1;
>>
>>       if (ffsox_stream_interleaved_write(so,pkt)<0) {
>>         DMESSAGE("writing packet");
>>
>> Maybe Carl Eugen can provide some insight into how to align the time
>> scales between streams.
>
> Your patch looks very wrong to me 

Obviously it is not wrong because it does the right thing :-) The 
question is why, because, of course, this patch is ad hoc without any 
understanding.

> but I only commented on a ffmpeg command line that you claimed shows a 
> problem with FFmpeg (it only showed an issue
> with the command line in question).
>
> I don't know what libffsox is.

It's a utility library where this code comes from.

    int ffsox_stream_interleaved_write(stream_t *s, AVPacket *pkt)
    {
       pkt->stream_index=s->stream_index;

    #if 0 // {
       fprintf(stderr,"%d: %I64d, %I64d\n",pkt->stream_index,pkt->pts,pkt->dts);
    #endif // }

       return av_interleaved_write_frame(s->fc,pkt);
    }


> One thing that comes to mind is: Is st->time_base the time_base of the
> input or the output stream? They do not have to be identical, not even
> if you requested them to be identical.

Stream "st" and codec context "cc" are output.

The packet "pkt" is constructed from a fresh frame which has no direct 
link to the decoded frame from the input, except sample frequency, 
number of channels, and channel layout.

>
> Carl Eugen
>

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