[mythtvnz] Best way to reduce CPU use (by ~10%) during software encoding/decoding

[Steven Ellis]

On 22/02/2009, at 10:46 AM, Aaron Whitehouse wrote:

> Hello,
>
> I have just upgraded my HTPC (to one based on the AMD 780G chipset, as
> mentioned in an earlier email). The weakest link in my new machine is
> the CPU, which is a Sempron LE-1200 (instead of the 2.4GHz P4 in the  
> old
> machine). While I thought the Sempron would be faster, it seems to be
> slightly slower at video encoding/decoding than the P4 was, meaning  
> that
> my current settings (512x576, 2200 bitrate, MPEG-4, quality between 2
> and 15, max 3 quality difference between frames, scale bitrate for  
> frame
> size, HQ encoding and 4MV), which worked fine in Live TV (i.e. one
> encoding stream, one decoding stream, no DCT encoding, no interlaced
> motion estimation) on the P4, are slightly too demanding for the new
> CPU. The new CPU is sitting at around 90+% in Top and is the video is
> quite jerky. I am guessing that the CPU is hitting 100% on occasion,
> stalling the playback.
>
> I have two cards in the machine - a bttv software encoder and a
> Hauppauge PVR-150 with MPEG-2 hardware encoding. I will probably  
> switch
> the default card to be the hardware encoder (MPEG-2 takes heaps of  
> room,
> but I have a new HDD), but I will still need to be able to record one
> hardware, one software and play one back. Playing MPEG-2 actually  
> seems
> to take slightly more CPU than playing back MPEG-4, which surprised  
> me.
>
> So here is my question (after all of that background): I only think  
> that
> I need to reduce CPU use by about 10%, but I am not sure which  
> settings
> are the best to change in order to get that. Disabling 4MV or HQ
> encoding saves a lot, but the picture isn't very good. Tweaking the  
> max
> and min quality makes some difference, but I'm not sure which to  
> change.
> What is the best thing for me to change?

HDs are cheap, sub NZ$200 for 1TB ex GST so go MPEG2.

If you want to upgrade your PVR150 for a PVR 500 let me know as I have  
some ex demo units from our myPVR demo boxes that i'm not using any  
more.

Steve



Steven Ellis - Technical Director
OpenMedia Limited
email   - steven at openmedia.co.nz
website - http://www.openmedia.co.nz

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