i3-7300T too slow to record-transcode a single HD-TV stream?

[MulziSAW 0]

Hi emby team!

 

I use the build in IPTV service (Telekom Entertain) and transcode recordings directly to .mkv to have a better streaming compatibility (skipping forward and so on).

 

This works fine for SD channels, but when recording a HD channel, the recordings are completely messed up. I used 'top' to check the CPU load of ffmpeg and it is around 200%. Having a i3-7300T with 2 cores and 4 threads, I think this means that ffmpeg is utilizing one core completely and that that isn't enough keep up with the stream. I tried the default ffmpeg version and a custom one (ffmpeg version 3.2.5-1) running on Debian GNU/Linux 8.9 (jessie).

 

So my questions are:

1. Shouldn't an up to date cpu be fast enough to transcode a single 720p stream?
2. I managed to get hardware decoding/encoding working for the normal transcodings - why isn't this working for record-transcodes?
3. Only one ffmpeg thread is running, although there are 2cores/4threads. '-threads 0' is used according to the log and shouldn't this setting use at least two threads?

I hope I didn't miss some important information.

 

Thanks for your help!

Mulzi

server-63648162999.txt

record-transcode-6ccbc483-5ac2-48c2-9152-fe729771ccf8.txt

[Luke 36991]

Does the recording complete successfully?

[MulziSAW 0]

Hey Luke,

 

thanks for looking into this!

 

Yes, it looks like the recording runs up to the end, but I'm not shure about the exit code.

[MulziSAW 0]

Anyone can answer one of those questions? I really would like to enjoy "Tatort" in 720p this Sunday evening 

 

I did some testing with ffmpeg and 'vaapi' and '-thread 2'. The following command (don't understand all parameters) produces a nice recording and uses only ~40% from 400% total cpu load (top).

/usr/bin/ffmpeg -async 1 -vsync -1 -fflags +igndts -analyzeduration 5000000 -hwaccel vaapi -hwaccel_output_format vaapi -vaapi_device /dev/dri/renderD128 -i "rtp://@239.35.10.1:10000" -t 00:01:00.000 -codec:v:0 h264_vaapi -force_key_frames "expr:gte(t,n_forced*5)"  -vf "format=nv12|vaapi,hwupload" -preset superfast -b:v 25000000 -maxrate 25000000 -bufsize 50000000 -vsync -1 -level 41 -fflags +genpts -map_metadata -1 -threads 2 -codec:a:0 aac -strict experimental -ab 320000 -sn -y "/RAID-Z1/Filme/Aufnahmen/test.mkv" 

If it helps I could also upload some raw stream data.

 

Thanks again!

Mulzi

[jacotec 7]

Hi Mulzi,

 

I'm using LiveTV in emby only for watching on the road via the TVHeadend Plugin, so my TVHeadend is doing all the recording stuff. But with TVH I've made the experience that the best option is to record with the "pass" profile which means that the recordings are saved to the disk in .ts format without transcoding.

 

With 4 parallel HD recordings from my SAT>IP tuners the CPUs of my TVH VM are just boring ...

 

Transcoding comes into place when needed while watching on the road. Watching on Kodi at home requires no transcoding at all.

 

If you have the option to record without transcoding also in emby and disk space is not an issue I'd recommend to go for this and use transcoding only when needed for watching.