no more hslv format ?

[MacFH - C E Macfarlane]

Please see below ...

On 02/05/2018 11:50, RS wrote:
>
> On 30/04/18 13:56, Jim web wrote:
>> I've been discussing the 'loss' of the 1280x720 25fps version with 
>> someone
>> at the BBC.
>>
>> IIUC this stemmed from 'Red Bee' days of yore, and until recently 
>> people at
>> the BBC had thought they had stopped it long ago. Someone apparently
>> noticed recently that it was still available. And then actually disabled
>> it. Hence the mysterious recent ending of its availablity.
>>
>> I have made the point that the 1280x720 25fps version is useful for 
>> people
>> with a content 'cap' problem, etc, so will be missed because the 50fps
>> version means somewhat bigger files and/or stream rates. But I doubt 
>> this
>> will cause a rethink.
>>
> We have known for some time that the BBC was going to stop using Flash 
> at some stage.  Dinky anticipated that change and get_iplayer no 
> longer supports Flash.  The last version with Flash capability was v2.99.
>
> HLS is a much more recent innovation than Flash.  get_iplayer now has 
> its own built-in downloader which downloads HLS 2 or 3 times as fast 
> as Flash.  HLS has been referred to as a legacy mode so it was always 
> likely that it would be removed eventually.  The surprise was that HLS 
> was removed at the same time as Flash.
>
> It is unrealistic to expect the BBC to restore HLS or Flash.

Yes, it' s unrealistic to expect the BBC to respond to any criticism 
whatsoever, because they never have in the past whenever changes they've 
introduced have broken other people's kit such as Network Media Players 
and Smart TVs.

> I have not seen any comments here which suggest that anyone is unhappy 
> with HVF.  get_iplayer uses the same built-in downloader as for HLS. 
> The BBC's full list of HVF modes is set out in a table in this document.
>
> https://www.bbc.co.uk/rd/blog/2015-07-the-development-of-new-video-factory-profiles-for-bbc-iplayer 
>
>
> What I think a number of people here would like to see is the addition 
> of one more High H.264 profile mode to that list, namely 1280x720p 25fps.

Not *necessarily*  -  I think the problem is more subtle than that. See 
below ...

> The BBC refers to viewing tests it has carried out, "using a range of 
> content and included clips, from popular shows such as Strictly Come 
> Dancing, East Enders and Top Gear."
>
> It concludes, "At around 3 Mbit/s a 960x540 profile at 50fps will be 
> made available to Connected TVs and set top boxes. The Elemental 
> encoders are used to convert the 1920x1080 interlaced content to 
> 960x540 for progressive encoding at 50fps. Although the 960x540 
> profile has a reduced spatial resolution compared to the outgoing 
> 1280x720 at 25fps, subjective assessments shows it delivers 
> significantly better pictures on TV screens across a wide range of 
> popular content (such as EastEnders and Top Gear) due to its higher 
> frame rate. The 50fps, 1280x720 profile, however, will be available to 
> those with 5Mbit/s broadband connections.

That's what I see as the problem, not a single natural history or art or 
historical documentary mentioned in the testing mix.  For such 
programmes, I would suggest that often an increase in spatial resolution 
would be preferable to an increase in temporal resolution.  I don't care 
how popular the above programmes are, I've not watched one of them in 
more than 20 years, and the other two ever.  The BBC is a public service 
broadcaster, and shouldn't only be thinking about what is best for 
populist programming.  They should be doing what is best for the content 
of a particular programme, or if that is too complicated and difficult, 
then, yes, let us have the choice of a 1280x720x25 profile, and let us 
choose which to download.

> I accept that there is a trade off between resolution and frame rate. 
> With differential encoding schemes like H.264, at a higher frame rate 
> the changes between frames are smaller, so there is less to encode. 
> Even so, for the uncompressed video the resolution at 50fps would need 
> to be reduced to 905x510p to give the same bit rate as 1280x720p at 
> 25fps.
>
> For that reason I find it surprising that 960x540p at 50fps "delivers 
> significantly better pictures on TV screens across a wide range of 
> popular content (such as EastEnders and Top Gear) due to its higher 
> frame rate" than 1280x720p at 25fps but the BBC has done the viewing 
> tests and I have not.
>
> More importantly BBC Four and to a lesser extent BBC 2 have a lot of 
> programmes about paintings, sculpture, architecture and nature where 
> there is a lot of fine detail and little motion. Intuitively such 
> programmes would not benefit from the higher frame rate but would 
> benefit from the higher resolution.  There is no mention in the blog 
> that such programmes were included in the viewing tests, and they 
> ought to have been.

Yes, agreed (I wrote the above before I'd read your post entirely, which 
was probably not best practice, for which apologies, but I'm in 
something of a hurry).

But there is also another elephant in the room, which is the capacity of 
their server system to deliver whatever they choose to do.  There's 
little point in increasing either spatial or temporal resolution if the 
resulting download will be compressed to hell on the way out of the 
servers.  I've seen even HD programmes break up into squares, possibly 
because the system can't cope with the throughput at times of peak 
demand, though I ought to point out in fairness that on at least one 
occasion the squares seem to be in the source programme, because 
downloading it a second time gave an identical result!

Regards.