[FFmpeg-user] HEVC decoding from multicast

[Ståle Kristoffersen]

Hi guys, this is a similar problem to one I had with h264, but this time it
is with HEVC. I'm trying to generate a thumbnail from a multicast stream
and I'm running into problems with hevc streams. I have written a small
program to subscribe to a multicast stream, and write out the video-pid to
disk and then run ffmpeg on it. On some streams the output will be mostly
gray (as in, they are missing some or most of their reference frames). One
possible solution is to have it capture more data and generate thumbnail
for a point in time a couple of seconds into the stream. While this works,
it slows down the process a lot, and I want it to be as fast as possible.
 
 
Here is an example file that does not work:
http://kolbu.ws/~chiller/hevcfail/hevcfail.ts [4672176 bytes]

When I run it like this:

$ ffmpeg -i hevcfail.ts -vframes 20 hevcthumb%02d.jpg

this is the output: http://pastebin.com/Z33Y3Aez and this is the files
generated: http://kolbu.ws/~chiller/hevcfail/thumb/ 

As you can see, hevcthumb01 through 16 is garbage, but from 17 and on they
look good. Is there a way to detect when a given frame has got all the data
it needs and will look ok? I would like to not decode more frames than
necessary, since decoding 4k HEVC is very slow on my computer.

I was going to make a bug report, but it seems like https://trac.ffmpeg.org is
down?

-- 
Ståle Kristoffersen
staalebk at ifi.uio.no