[mythtvnz] Transcoding HD videos

[Nick Rout]

On Sun, Apr 22, 2012 at 8:52 PM, Pshem Kowalczyk <pshem.k at gmail.com> wrote:
> Hi All,
>
> I was wondering if anyone transcodes Freeview|HD stuff into something
> less diskspace hungry? I came up with the following set of parameters
> for ffmpeg for HD material (1080 to 720 and reducing the bitrate to
> about 3.5Mb/s from original 10-11Mb/s, retaining the orginal mpegts
> format and removing 'unknown' streams):
>
> ffmpeg -i /data/mythtv/store/4003_20100206192900.mpg -threads 3 -map 0
> -c copy -c:v:0 libx264 -s 1280x720 -map -0:3  -b:v 3500k -pass 1 -f
> rawvideo -an -y /dev/null
> ffmpeg -i /data/mythtv/store/4003_20100206192900.mpg -threads 3 -map 0
> -c copy -c:v:0 libx264 -s 1280x720 -map -0:3  -b:v 3500k -pass 2 -f
> mpegts /data/mythtv/store/4003_20100206192900.mpg.new
>
> (after that I use mythcommflag --rebuild to rebuild the index so myth
> can play it)
>
> Unfortunately every now and then (roughly every 5-10 minutes) the
> scene change is not smooth, as if the key frame got missed. It's not
> terrible, but decreases the WAF a little bit every time it happens.
> Anyone doing this sort of  transcoding? If so - what do you use?
>
> kind regards
> Pshem
>

I understand current x264 best practice is to use constant quality
with one pass. Seems to be what they suggest on doom9 and similar
forums.

whether it applies to the files we are dealing with is unknown to me.