[pvrusb2] Comparison of Video Stream Bitrates

[Roger]

On Thu, 2009-05-21 at 21:16 -0500, Mike Isely wrote:

> It's not a real comparison.
> 
> To compare them fairly you have to compare them in digital mode.  In 
> that case both the HVR-1950 and the HDHomeRun will just grab a bit 
> stream from the RF signal.  IN DIGITAL MODE THERE IS NO CAPTURE OR 
> ENCODING TO BE DONE.  The "encoding" such as it is comes from the 
> transmitting station, or possibly even the station's upstream source 
> depending on the program.  All that the two devices do in this case is 
> grab the bits out of the carrier and pass the resulting stream to 
> whatever app is reading from them.  The bit rate and quality will be 
> exactly equal.
> 
> Electrically, a digital TV "capture" device is actually simpler than its 
> analog version.  With an analog capture device, one must:
> 
> 1. Tune the signal.
> 2. Demodulate it to get the analog baseband video signal
> 3. Do A/D conversion to capture the analog signal into a frame buffer
> 4. Perform encoding on the frame to generate the mpeg signal
> 
> The HVR-1950 in analog mode does all of the above.  A non-encoding 
> analog capture device will do all of the above except step 4.
> 
> However a digital signal is much simpler.  Basically after step 2 
> instead of baseband you get a bit stream.  So a digital capture device 
> need only do:
> 
> 1. Tune the signal.
> 2. Demodulate it to get the digital bit stream
> 
> The HVR-1950 in digital mode only needs to do the above.  The same is 
> true for the HDHomeRun and for EVERY other digital capture card.  

Duh.  I'm getting so stupid.  Guess it's because I'm spending more time
away from the computer and working on the house!  I knew all this
already!

> So if you're comparing an HDHomeRun to an HVR-1950, then they are not 
> comparable at all in analog mode, and in digital mode they will always 
> be exactly equivalent.

This is what I was doing all day that day... comparing HDHomeRun &
HVR-1950.  Finally came across one poster stating he didn't want the
excess traffic on his 100 Mb/sec network.

I too somewhat agree at times as I prefer quick access to the Internet,
even though everybody states it's a minimal load.

Also, I've had great success with video capture via USB as it's more
reliable when compared to using the network.

To include, the HDHomeRun <v1 didn't do EIT for EPG data for MythTV.
Unknown as to whether the HDHomeRun >v2 does, but one posts declares it
disfunctional within MythTV.

So, I ordered the HVR-1950 as some say EIT for EPG data does work. 

I'm guessing why most grab an HDHomeRun, is for the dual tuners.  Which
would be another great feature for the PVRUSB2/HVR-1950 as sometimes I
do want to watch another channel while recording.

> The "ideal" capture device would be an HVR-1950 that has an HD 
> capture capability like the HD-PVR for analog (but still also have the 
> analog tuner).  As far as I know no such device exists on the market.  
> Given the fact that analog broadcast TV in the USA is not long for this 
> world now, a device like that will probably never appear.  It would 
> probably be horribly expensive anyway.
> 
>   -Mike

Echostar frequents this route.  But they attempt to lock-down their h/w
using proprietary code along with hack-proofing things for some odd
reason.

Since I'm still stuck in the 2x750P3 w/ 1GB RAM era, and will be for a
long time, I think it would be a really neat feature to have an on-board
video resize function (ie. Hi-Def to Standard Definition resize).  But,
again, I doubt this as it would deter newer CPU/Motherboard sales. :-/


-- 
Roger
http://rogerx.freeshell.org