GPU re-encoding?

I'm really impressed with the app and for most of my videos it works wonderfully. Unfortunately I'm having some problems with 1080p videos (H.264, mkv).

The player on the iphone stops to buffer every 2 minutes or so, and I assume it's because my CPU can't keep up. It also lowers the bitrate when it buffers. Is the lowering of the bitrate a bug? Because 720p videos play fine even at 2 mbps so the bandwidth is not the problem. Or does lowering the live conversion bitrate help on the server side re-encoding too? In any case, with 1080p videos even when the bitrate is 256 kbit/s it buffers every couple of minutes.

An option would be to do offline conversion but I understand that this fixes the bitrate so it wouldn't work well over the internet (specially over 3g). Is this correct?

Another solution on my end would be to get a faster CPU (it's a 5 years old AMD afterall) but my setup works perfectly for everything else. I'm able to watch any video on the desktop because of decoders, such as CoreAVC and the MPC-HC decoder, that use my GPU (GTX 260). Now of course I wouldn't expect inmethod to develop a GPU decoder but ideally it could use an existing one on my system or I guess bundle one with the server application as I understand things are currently self-contained. I also understand that you use ffmpeg, though I'm not sure what their status is with GPU decoding/encoding.

thanks!

Hi,

there's no support for HW accelerated decoding. Given that Air Video uses ffmpeg, which is very self-contained, invoking other (system-wide) codecs to decode the file would be quite difficult.

The lowering of quality that you experiences is probably caused by server side encoding delays, which the client mistakes for lack of network bandwidth (thus lowering the quality).

I'm afraid there's not much you can do right now apart from upgrading your CPU.

Admin wrote:Hi,

there's no support for HW accelerated decoding. Given that Air Video uses ffmpeg, which is very self-contained, invoking other (system-wide) codecs to decode the file would be quite difficult.

The lowering of quality that you experiences is probably caused by server side encoding delays, which the client mistakes for lack of network bandwidth (thus lowering the quality).

I'm afraid there's not much you can do right now apart from upgrading your CPU.

FFmpeg seems to support hardware accel in new builds. Nvidia PureVideo on Linux and I think DXVA on Win32 ? Maybe it's just a matter of enabling configure options ?

Don't have the hardware here to test it here :/

corepl wrote:

FFmpeg seems to support hardware accel in new builds. Nvidia PureVideo on Linux and I think DXVA on Win32 ? Maybe it's just a matter of enabling configure options ?

Don't have the hardware here to test it here :/

DXVA support would be perfect.. please admin, any chance of enabling that option in FFmpeg?

mach411 wrote:

corepl wrote:

FFmpeg seems to support hardware accel in new builds. Nvidia PureVideo on Linux and I think DXVA on Win32 ? Maybe it's just a matter of enabling configure options ?

Don't have the hardware here to test it here :/

DXVA support would be perfect.. please admin, any chance of enabling that option in FFmpeg?

I'm really not sure what the status of DXVA support in ffmpeg is. If it is stable we could try to make a build with dxva enabled at some point, however right now we're quite busy with higher priority features.

That said, the ffmpeg source code used in air video is publicly available, anyone can try to make a build with dxva enabled. However building ffmpeg under windows is quite tricky.

One question:
Is it possible to somehow disable the reencoding, since this really is a pain in the b*tt.

If there's one hickup in the live conversion it immediately starts reencoding to a really really crappy quality which
is basically unusable.

So I could live perfectly with an occasional rebuffering but not with the crappy reencoding.

So can't this be somehow disabled on the client- or the server-side?

This message was edited 1 time. Last update was at 03/12/2010 21:13:02

You can disable the bitrates. In iPhone App go to conversion settings -> Global conversion and disable all bitrates except 1.5mbit/s. If you want to stream over 3G you might want to leave another bitrate enabled (i.e. 384kbit/s) as 1.5mbit/s will likely be too much.