HD-PVR encoding question

[wayner]

Does the HD-PVR use a lower bitrate for capturing 480i (or 480p) content as opposed to 1080i content?

I generally only use my older analog capture card for recording SD content but I then transcode it to an MPEG-4 variant. Would I be better off just capturing it with my HD-PVR at a lower bitrate as I will end up with an H.264 file anyway?

My objective is to create a file that is not too large without having to do reencoding. This would facilitate uploading the file to my seedbox so that I could download it to my laptop when I am on the road travelling. I could then watch then content without having to be online - kind of like Placeshifter with no internet connection required.

In other words how would the file compare if I captured with the Fair-H.264 setting that is 1.8GB/hr compared to capturing a file in regular MPEG-2 and then reencoding it to an MPEG-4 AVI or MKV that was also about 1.8 GB/hr?

[Rico66]

You can control this via SD Capture Rate under HKLM\Software\Frey Technologies\Common\DirectShow in the registry.
This factor scales the SD capture down by a given factor. The default is 25, which scales by 2.5 (25 divided by 10)

[Spectrum]

Recording using a 1.8GB/hr will theoretically give you a better picture than recording at a higher bitrate then re-encoding because; only goes through one lossy compression step rather than two. Whether you will notice a difference is another matter all together

[wayner]

Originally Posted by Rico66

You can control this via SD Capture Rate under HKLM\Software\Frey Technologies\Common\DirectShow in the registry.
This factor scales the SD capture down by a given factor. The default is 25, which scales by 2.5 (25 divided by 10)

Does this only apply to recordings on the HD-PVR or does it also affect MPEG-2 recordings via S-video or OTA?

[Rico66]

Originally Posted by wayner

Does this only apply to recordings on the HD-PVR or does it also affect MPEG-2 recordings via S-video or OTA?

Afaik it's specific to hdpvr/Colossus.

[wayner]

Originally Posted by Rico66

You can control this via SD Capture Rate under HKLM\Software\Frey Technologies\Common\DirectShow in the registry.
This factor scales the SD capture down by a given factor. The default is 25, which scales by 2.5 (25 divided by 10)

One more question - I assume that this then mean that the bitrate/filesize is divided by 2.5 for this setting. In other words, if you had selected the Fair-H.264 1.8GB/hr setting then does this mean that by default that the fizesize will be 1.8/2.5 or 0.72GB/hr?

Why is the default 2.5 rather than a number like 6? Doesn't 1080i contain 2,073,600 pixels per frame (1080*1920) while 480i contains 307,200 (640*480) pixels per frame which is a ratio of 6.5:1?

edit - I have made sure that this registry entry is set to 25 and I am trying to record a show from an SD channel on my HD-PVR to see what filesize I get.

[wayner]

I tried this today and it didn't work as expected since the quality was set to H.264 Fair - 1.8GB/hr. Therefore if it divides by 2.5 for SD content then should the encoding be about 700MB per hour? I go 770MB in half an hour. Note that the file is 480p.

Here is the output from the Sage web server:

Duration: 30 m
 
Channel: 429-SETANTC

Category: Sports non-event - Rerun
 
Original Air Date: Monday, January 10, 2011
 
Show ID: SH013752360000
 
Encoded by: Hauppauge HD PVR Capture Device Fair-H.264
 
File Format: MPEG2-TS[H.264 16:9 480p@60fps, Dolby Digital/192Kbps@48kHz Stereo]
 
Files: 
\\carnoustie\media2\tv\SetantaConnected-4058669-0.ts 

File Playlists: [wvx] [m3u] [pls] 


Size: 0.77GB