no more hslv format ?

[Nick Payne]

On 3/05/2018 9:24 AM, RS wrote:
> On 02/05/18 23:21, Owen Smith wrote:
>
>>
>> I've been mystified for a while why people talked about "dropping
>> every other frame" as if it were trivial to do, and an email earlier
>> in this chain looked like someone was trying to do that again. I was
>> explaining why that simply is not possible in the general case.
>>
>
> If I have caused confusion by talking about dropping alternate frames
> I apologise.  I had come across some posts in another forum which
> suggested it could be done, but I now recognise I was wrong.  What
> makes it worse is that I have since come across a thread in this
> listserver from two years ago where I was asking exactly the same
> questions, and Vangelis pointed out I was wrong and directed me to a
> Wikipedia article on H.264.
>
> It is not possible to change the frame rate using -c:v=copy in ffmpeg;
> it is necessary to re-encode which is why it takes so long. 
> Inevitably there will be losses, added to which the codecs available
> to us may be inferior to those used by the BBC.
>
> I think it was Nick Payne who said he had experimented with
> re-encoding in HEVC (H.265) and found that the file size was the same
> for 25fps as it was for 50fps, which led him to conclude that frames
> were being duplicated to achieve 50fps.

Yes, I had some of the coverage of the UK snooker championships where
they provided HLS downloads @ 1280x720 25fps and other coverage was only
available as HVF downloads @ 1280x720 50fps. When I ran these both
through Handbrake with identical settings to convert to HEVC, retaining
the frame rate of the downloaded files, the size reduction for the 50fps
downloads was about twice that for the 25fps downloads, and the size of
the files output by Handbrake was proportional to the length of the
program and not the frame rate. e.g.

4h58m match: D/L size 5.03Gb @ 25fps, output from Handbrake was 1.55Gb
4h44m match: D/L size 10.2Gb @ 50fps, output from Handbrake was 1.48Gb

Nick