[FFmpeg-user] problem of transcoding HD DVB-T program

Andy Furniss adf.lists at gmail.com
Thu Jun 12 13:15:06 CEST 2014

Soundwin / Andy wrote:
> Hi guys, this is my first time to use the ffmpeg mailing list.
> I modify the DVR_BUFFER_SIZE  of drivers/media/dvb/dvb-core/dmxdev.h
> to 10000*188*1024 (original is 10*188*1024) due to HD program issue.

Years ago I played around with settings like this when making dvbtraffic
record a whole mux to disc - I've never dome it WRT tzap/ffmpeg.

The fact you need to set it huge impliess your box isn't reading fast
enough - I know setting bigger can help, but dvb will drop the whole
buffer if it fills so you loose a bigger chunk when that eventually happens.

If tzap logs when the read fails a read maybe you could match that with
ffmpeg getting confused.

Maybe there are things you can do with your setup like set cpu(s) to
perf if cpufreq is running. If there are other things happening that use
disk heavily I suppose they could affect it.

> So, I can use tzap and ffmpeg to stream the HD program now.
> However, I use the command to stream program
> /usr/bin/tzap -a 1 -c /home/andy/channels.conf -o - -r -p "D" |
> /home/andy/ffmpeg -f mpegts -i pipe:0 -c:v libx264 -preset medium
> -crf 23 -bufsize 3000K -minrate 1200k -maxrate 1200k -pix_fmt yuv420p
> -g 50 -s 1024x768 -acodec libmp3lame -b:a 128k -ac 2 -ar 44100 -f
> mpegts udp:// &
> The command always make troubles, after a random time(within 60
> minutes), the transcoding process will be abnormal.
> The ffmpeg doesn't stop, but it drops all frames, and no video
> output.

You should normally post full uncut ffmpeg console output to the list -
of course it it's huge the beginning and end when it fails would
probably be OK.

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