On 16/04/18 09:27, Nick Payne wrote:
On 16/04/2018 5:21 PM, Steve Dodd wrote:
On Sun, Apr 15, 2018 at 9:59 PM, Nick Payne <njh...@gmail.com> wrote:

I experimented a while ago with running some GiP downloads through
Handbrake to convert the video to the x265 codec. That reduced the file
size to about 1/3 of the original download, with no subjective
difference in video quality that I could see when viewing on our TV.
Figures - most of the comparison work done on H.265 v. H.264 says you
should get same subjective quality for half the bitrate.

A one hour 1280x720 25fps program that downloads as a 1Gb file was reduced
in size to ~350Mb. On my PC, the re-encode runs at about 50fps for
1280x720, so ~2x real time for 25fps and ~real time for 50fps. For
smaller video dimension such as 960x540, the re-encode speed was around
85-90FPS.
Do you know what x265 quality setting you used? I'm also experimenting
now it seems HLSHD is being turned off (series 2 of Salamander has HVF
only so far).. RF17 seems to be spitting about half the bitrate of the
BBC h.264 output, and running at ~40fps which I can live with (Core
i5-6500). Noticeable quality difference still when looking at stills,
but have tried watching it moving yet..
For re-encoding 1280x720 downloads to x265, on the Video tab in
Handbrake I have the encoder preset at "Faster" and the RF quality at 23.

I tried using ffmpeg and the libx265 codec with default quality (CRF=28?) on HVFhd. I only did half a minute because it was so slow. It is convenient to do it on this machine, but it has only got a 2.3GHZ Core 2 duo. I set -r=25 to reduce the frame rate to 25fps by dropping alternate frames. It confirmed that dropping frames worked, and I did not notice any problems as a result. It only processed 2 frames a second, so an hour's recording would take 12 hours! I'll have to try it on my latest laptop which has a core i5-7200U.

Best wishes
Richard


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