RFC - bring back fast channelswitch

[whaupt]

We need to upgrade to OpenELEC 5.95 in order to fix a problem.
When testing I found that the channel switching is up to 5sec again.

I know the code is there for a reason, so maybe we can discuss possibilities to bring it back again.

[a1rwulf]

My findings:
iformat was always NULL for my tests with udp, http and some radio streams.
So this check does always set streaminfo to true, while the DVDDemuxFFmpeg::Open is called with streaminfo = false for pvr, tcp and udp streams.

[whaupt]

Seems some users are affected too:
http://forum.kodi.tv/showthread.php?tid=235178

[Jalle19]

@FernetMenta

[FernetMenta]

this will break other formats. you only can skip streaminfo for mpegts live streams.

[whaupt]

Thanks for clarifying, I thought it would break something...
Is there another way we can detect if it's a mpegts stream other than using iformat->name (because it is NULL for some reason)?

[FernetMenta]

NULL for some reason

what reason?

[whaupt]

I don't know.
Tried to investigate because I always thought that it is filled corretly on avformat_open_input, but this is not the case - I did also check version 13.2 where we worked on the fast channelswitch patches once: #3590
iformat is also NULL there.
This check was added shortly after this time and seems to jave removed the fastswitch again.

[FernetMenta]

I don't know.

investigating is the first step towards a possible solution. as long as we don't understand it, we can't fix it

[whaupt]

I did already try to find out how it is supposed to work.
According to ffmpeg docs avformat_open_input is not meant to fill iformat:
https://www.ffmpeg.org/doxygen/2.5/group__lavf__decoding.html#ga10a404346c646e4ab58f4ed798baca32

Do you know where kodi detects the video format of a stream or where I can start looking?

[FernetMenta]

Do you know where kodi detects the video format of a stream or where I can start looking?

most work is done in CDVDDemuxFFmpeg::Open
There are many different cases we support and I don't know any details of yours. Some input streams set mime type to determine format, other do low level probing.

[whaupt]

I will dig into it and see what I find.

[whaupt]

I think this is obsolete.
We patched it for our needs and it there is also a forum discussion in the new VideoPlayer forum section.