[mythtv-users] HEVC/H.265 playback

[Leo Butler]

Stephen Worthington <stephen_agent at jsw.gen.nz> writes:

> On Wed, 21 Apr 2021 11:45:27 -0500, you wrote:
>
>>Hi,
>>
>>I briefly did some experimenting with transcoding recordings using
>>libx265+ffmpeg in an mpegts container.
>>
>>While the transcoding was fine and playback is fine over my lan using
>>ffplay on my (old, slow) laptop, on my dedicated frontend only cartoons
>>playback ok; other transcoded recordings have a lot of stutter and are
>>unwatchable. I will guess that this is because the dedicated frontend is
>>about 8 years old and has a slower cpu [*,**].
>>
>>I wonder if anyone has experience in these matters? Would a graphics
>>card be an option (the frontend has a couple low profile pci-e slots
>>available)? I am using ubuntu 20.04 and v0.31/fixes from the mythbuntu
>>ppa, if that matters.
>>
>>TIA,
>>Leo
>
> Playing H.265 using just the CPU takes a lot of CPU, and I suspect
> that it needs to be mostly one core only doing the work.  I had
> similar problems to yours with my main MythTV box which was using an
> Nvidia GT220 card, which is far too old to do H.265.  After I upgraded
> it to an Nvidia GT1030 which has native H.265 support, and also
> upgraded MythTV to v31 which has the big rendering changes that
> brought support for H.265 offloading to the GPU, I have no problems
> with H.265 videos.  And also as a bonus I found that playing 4K video
> in H.264 and H.265 worked on my 1080p only screen - the GPU seems to
> be doing the downscaling.
>
> Depending on how old the frontend box is, it is likely to be only PCIe
> 2.0 or 2.1.  Pretty much all modern graphics cards are now PCIe 3.0
> (or better).  The low end ones are typically PCIe 3.0 x4, even though
> they still are built for a x16 socket.  They just do not use the other
> 12 PCIe lanes - the pins are not connected.  A rare exception is an
> EVG card with an Nvidia GT1030 that I bought which uses a x4 socket
> for its x4 connection, and can be used in any x16, x8 or x4 socket.
>
> This has come about because with PCIe 3.0, a 4 lane (x4) connection is
> fast enough to max out the transfer rate of the GPU.  But if you plug
> these cards into a PCIe 2.0 or 2.1 motherboard, since they have only 4
> lanes, they can not max out their transfer rate at PCIe 2.0 or 2.1
> speeds and so potentially will not perform as well as an older
> graphics card that is PCIe 2.1 x16 and uses all 16 lanes.  This only
> matters for things other than MythTV though - heavy graphics programs
> and games where there is a huge amount of data being sent to the GPU.
> For MythTV where the rendering is being offloaded onto the GPU, the
> data transfer rate is very low - the same rate as the video stream in
> the recording or video file.
>
> So, for upgrading your frontend, as long as it is not being used for
> other graphics intensive things as well, I would recommend the
> cheapest modern Nvidia card, a GT1030 model.  There are several that
> are fanless which is a bonus as they will last forever - I have yet to
> have any fanless Nvidia card die.  Cards with fans usually die much
> earlier when the fan(s) fail.  The downside of the GT1030 is that its
> 4K support is limited, but they are reasonably cheap.  There is likely
> a similar spec Radeon card available also, but I have never used
> Radeons so I do not know anything about their current range.
>
> The Asus and EVGA silent GT1030 cards I have all came with an low
> profile bracket in the box.

Thank you, Stephen. I'll see how that Asus GT1030 card works out.

Leo