[FFmpeg-devel] make work (live) libsrt

[Marton Balint]

On Sat, 25 Aug 2018, Tudor Suciu wrote:

> Hello,
>
> Is this patch in a better shape for inclusion?

The code seems OK, please resend the patch with a docs/protocols.texi 
update for the new option.

Thanks,
Marton


>
> Regards,
>
> On Fri, Aug 24, 2018 at 2:46 AM mypopy at gmail.com <mypopy at gmail.com> wrote:
>
>> On Fri, Aug 24, 2018 at 2:55 AM Marton Balint <cus at passwd.hu> wrote:
>>>
>>>
>>>
>>> On Thu, 23 Aug 2018, mypopy at gmail.com wrote:
>>>
>>>> On Wed, Aug 22, 2018 at 4:30 AM Tudor Suciu <tudor.suciu at gmail.com>
>> wrote:
>>>>>
>>>>> Hello,
>>>>>
>>>>> I get errors when I try to send a live srt stream that the first
>> packet is
>>>>> too big:
>>>>> 21:30:39.896626/ffmpeg*E: SRT.c: LiveSmoother: payload size: 1504
>> exceeds
>>>>> maximum allowed 1316
>>>>>
>>>>> Here are example commands for server and client:
>>>>> ffmpeg -re -i ~/Downloads/ToS-4k-1920.mov -vcodec libx264 -g 50 -refs
>> 1 -s
>>>>> 640x360 -b:v 1000k -acodec aac -b:a 64k -flush_packets 0 -f mpegts
>> "srt://
>>>>> 127.0.0.1:5555?mode=listener"
>>>>> ffplay srt://127.0.0.1:5555
>>>>>
>>>>> A patch that fully solves the issue is:
>>>>> diff --git a/libavformat/libsrt.c b/libavformat/libsrt.c
>>>>> index 0f9529d263..156a4776e2 100644
>>>>> --- a/libavformat/libsrt.c
>>>>> +++ b/libavformat/libsrt.c
>>>>> @@ -412,6 +412,8 @@ static int libsrt_open(URLContext *h, const char
>> *uri,
>>>>> int flags)
>>>>>          return AVERROR_UNKNOWN;
>>>>>      }
>>>>>
>>>>> +    h->max_packet_size = 1316;
>>>>> +
>>>>>      /* SRT options (srt/srt.h) */
>>>>>      p = strchr(uri, '?');
>>>>>      if (p) {
>>>>>
>>>>> How would you like this option to be made work in a way that can be
>>>>> accepted in ffmpeg?
>>>>> Is there a way to change the max packet size without this patch?
>>>>>
>>>> In your case, I don't think hard coding max packet size == 1316 is not
>>>> a good idea in loopback device, and after deep in the srt
>>>> library(https://github.com/Haivision/srt) source code, I think srt
>>>> library need to fix the hardcode about packet size limition.
>>>
>>> I can't think of a scenario where limiting the packet size actually
>> causes
>>> problems, but if you insist on not limiting it in general, then the max
>>> packet size should be settable using an option, same way it is for UDP.
>>> (pkt_size option). I'd suggest using 1316 as default, because that
>>> is the more common (and currently the only working) use case...
>>>
>>> Thanks,
>>> Marton
>> I agree with you, giving an option like pkt_size and using 1316 as the
>> default in this case is a better way to fix this issue.
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>>
>