Variable Bit Rate Settings

[Crowdx42]

Hi again.
just wondering is the PVR 250 recording default variable or constant bit rate and if it is constant how well does it work at variable bit rates? What has given you guys the best picture vs disk space?
I know this has been asked before but I am wondering what is the better way to do things, I currently record at 3.25gig per hour but also see a BEST setting at 3 gig, is it a variable bit rate?
Any insight would be very much appreciated.
Thanks
Patrick

[TunaBoo]

The 3.25 gigs is a DVD format (i.e. you can shove it on a DVD and play in a DVD player) while the 3 gig "best" is just a straight mpeg stream. I think the 3 gig works better than the 3.25 gig, as long as you don't need to burn.

Almost all video is VBR, but most audio is not. If I had to guess, I would guess both were doing VBR video and CBR audio, but I am too lazy to look it up. Someone else will jump in.

[nielm]

I thought that all video settings are CBR. VBR modes have to be deifned manually:
http://www.freytechnologies.com/HPquality.txt

[Crowdx42]

Ok, I tried the link that nielm posted but when I put in one of the examples into the Sage 2 properties file it does not show in Sage when I start the program. When I edit the properties file Sage is not running and the edit in the file shows up when I open it, it just is not showing in Sage when I view detailed setup and try to set the quality settings. Anyone know about this in Sage 2?
Patrick

[mlbdude]

For the Hauppauge 250 most or all are VBR last I heard. I had to manually create some CBR entries.

Make sure you add BOTH lines to your properties file when Sage is closed.

[Crowdx42]

BOTH lines?
What I did was copy and paste one of the examples on nielm's link, what second line do I need to add?
Patrick

[nielm]

did you add both properties lines? there should be a line
mmc/python2_encoding/<name>
defining the parameters for the encoder and another line
seeker/recording_qualities/<name>
referring to it...
Someone has got a 2.35 CBR bitrate mode workign with 1.4.10 in in this forum post -- you may use this as a sample

(getting a custom VBR mode is on my todo list!)

[Crowdx42]

Ok,, that got it.. gonna play with it later and see the differences.
Thanks
Patrick

[Opus4]

So... according to the Hauppauge site, the default recording rates do seem to be VBR. But, does anyone know what their equivalent mmc/python2_encoding settings would be? These defaults seem to be internal to either the encoder drvier or SageTV. Is this info listed somewhere & I haven't found it yet? The Hauppauge site has a table to show approx. file sizes for an hour's recording & a couple people have used trial & error to guess at the settings, but is the actual answer listed anywhere?

Also, when using VBR, there are 2 bit rate settings: videobitrate and peakvideobitrate. Just to clarify: peakvideobitrate is obviously the max rate allowed, so does videobitrate correspond to the min rate to be used, as seems likely?

- Andy

[DFA]

Hi:

Opus4:
I can't answer your question because I have too many of my own.

In principle, I understand the conceptual difference between VBR and CBR, but with out knowing all the nuts and bolts and how it is implemented (especially VBR), there is no inherent and intuitive way to know which might yield better quality

I've been doing some searching here, AVS and SHS forums looking for a definitive answer about whether CBR or VBR gives better quality. I have found the question asked more than once, but no solid replys. Forget about disk conservation, burning to DVD's or whether the material has a lot of action and motion or not. Just want to know what gives best results, disk space be damned and no consideration to the source material. So far, the responses I have found dance around the question.

I have recently chosen the "MPEG2 Max Quality - 5.6 GB / hr" setting in Sage but was wondering if this is CBR or VBR? And if truely the "Max Quality", the better of the two (VBR ro CBR) would be used in that selection I should think.

EDIT: It seems VBR is supposed to be a more efficient mode. If CBR and VBR were compared where the CBR bit rate is equal to the VBR PEAK bit rate, the ability for the VBR to be of equal quality would seem to depend on the criteria for stepping up and stepping down the bit rate for VBR. On the other hand, if the CBR bit rate were equal to the VBR BASE (minimum) bit rate, it seems reasonalbe to conclude that VBR would have the advantage because of the ability to modulate above the base rate.

And as a point of speculation, if I configure VBR for the peak bit rate to be equal to the base bit rate, that would in essence make VBR --> CBR!

Anyway, probably more to it than that and would like to hear what the more knowledgable have to say.

DFA

[kny3twalker]

actually the properties defined by sage are CBR
in the web page Frey says VBR is off by default

I added a bunch of VBR to mine

also in v1.4 this could be tested by using the window that poped up
change the recording quality of shows you are watching and it is setup accordingly

yes hauppauge's were VBR accept when stating they were CBR but Frey's properties are defined on their own

anyways anyone that wants to argue whether SageTV's default are VBR or CBR we can do that but here are some properties that I made up
to add VBR rates to the default CBR rates (not overwriting the old ones though)

mmc/python2_encoding/Best\ -\ Variable\ Rate=videobitrate\=5000000|width\=720|height\=480|
audiobitrate\=384|vbr\=1|peakvideobitrate\=7500000

mmc/python2_encoding/Fair\ -\ Variable\ Rate=videobitrate\=2000000|width\=720|height\=480|
audiobitrate\=384|vbr\=1|peakvideobitrate\=3000000

mmc/python2_encoding/Good\ -\ Variable\ Rate=videobitrate\=3000000|width\=720|height\=480|
audiobitrate\=384|vbr\=1|peakvideobitrate\=4500000

mmc/python2_encoding/Great\ -\ Variable\ Rate=videobitrate\=4000000|width\=720|height\=480|
audiobitrate\=384|vbr\=1|peakvideobitrate\=6000000

mmc/python2_encoding/Highest\ Quality\ -\ 4.25GB\ per\ hr=videobitrate\=9500000|width\=720|height\=480|au
diobitrate\=384
mmc/python2_encoding/Highest\ Quality\ -\ Variable\ Rate=videobitrate\=6000000|width\=720|height\=480|
audiobitrate\=384|vbr\=1|peakvideobitrate\=9000000

mmc/python2_encoding/MPEG2\ Max\ Quality\ -\ Variable\ Rate=videobitrate\=9000000|width\=720|height\=480|
audiobitrate\=384|vbr\=1|peakvideobitrate\=1257500
0


seeker/recording_qualities/Best\ -\ 3GB\ per\ hr=Best,384,48000,6666666
seeker/recording_qualities/Best\ -\ Variable\ Rate=Best - Variable Rate,384,48000,7500000
seeker/recording_qualities/CVD\ ~\ 1.4GB\ per\ hr=CVD,224,48000,3000000
seeker/recording_qualities/DVD\ Extra\ Long\ Play\ ~\ 1.8GB\ per\ hr=DVD Extra Long Play,384,48000,4125000
seeker/recording_qualities/DVD\ Long\ Play\ ~\ 2.5GB\ per\ hr=DVD Long Play,384,48000,5750000
seeker/recording_qualities/DVD\ Standard\ Play\ ~\ 3.25GB\ per\ hr=DVD Standard Play,384,48000,7250000
seeker/recording_qualities/Fair\ -\ 1GB\ per\ hr=Fair,256,48000,2222222
seeker/recording_qualities/Fair\ -\ Variable\ Rate=Fair - Variable Rate,384,48000,3000000
seeker/recording_qualities/Good\ -\ 1.5GB\ per\ hr=Good,256,48000,3333333
seeker/recording_qualities/Good\ -\ Variable\ Rate=Good - Variable Rate,384,48000,4500000
seeker/recording_qualities/Great\ -\ 2GB\ per\ hr=Great,384,48000,4444444
seeker/recording_qualities/Great\ -\ Variable\ Rate=Great - Variable Rate,384,48000,6000000
seeker/recording_qualities/Highest\ Quality\ -\ 4.25GB\ per\ hr=Highest Quality - 4.25GB per hr,384,48000,9500000
seeker/recording_qualities/Highest\ Quality\ -\ Variable\ Rate=Highest Quality - Variable Rate,384,48000,9000000
seeker/recording_qualities/MPEG2\ Max\ Quality\ -\ 5.6GB\ per\ hr=MPEG2 Max Quality,384,48000,12575000
seeker/recording_qualities/MPEG2\ Max\ Quality\ -\ Variable\ Rate=MPEG2 Max Quality - Variable Rate,384,48000,12575000
seeker/recording_qualities/SVCD\ Extra\ Long\ Play\ ~\ 0.75GB\ per\ hr=SVCD Extra Long Play,224,44100,1725000
seeker/recording_qualities/SVCD\ Long\ Play\ ~\ 1GB\ per\ hr=SVCD Long Play,224,44100,2175000
seeker/recording_qualities/SVCD\ Standard\ Play\ ~\ 1.2GB\ per\ hr=SVCD Standard Play,224,44100,2575000

also just to add this no matter if the recording quality is setup to be CBR or VBR
CBR is not perfect and the bit rate does still vary

[DFA]

kny3twalker:

Thanks for those, I think I'll plug them in for the wider selection.

No interest here in debating who is using what, just interested in what theoretically is the better choice; CBR or VBR, all other things being equal.

DFA

[kny3twalker]

it depends on the subject matter that you are recording
is all I can say

what tyoe of recording are you having trouble with?
I used different recording qualities for alot of my recording
for sports based material and my default (so in case I change to a sporting event)
I use my quality Max Quality 5.6 GB per hr Variable Rate

[Opus4]

Originally posted by kny3twalker
actually the properties defined by sage are CBR
in the web page Frey says VBR is off by default

Where are you seeing that the Frey settings are CBR? The doc for how to create custom settings says the default is VBR to be off, but that doesn't mean the standard ones use CBR; it just means that if you don't specify CBR/VBR when you create a custom setting, then VBR will be off.

Did you see another reference to this? If so, could you post a link?

here are some properties that I made up
to add VBR rates to the default CBR rates (not overwriting the old ones though)

Why don't you simply add a section to the FAQ thread with a question for any example custom recording rate settings, then reference a new thread that includes the ones you made & perhaps others can add their own. That way, you wouldn't find yourself posting those same settings every so often. I liked having them as examples, but that would make it easier for new people to find them.

--------------------------------------------------------------------

Anyway... the question still stands: does anyone know the equivalent mmc/python2_encoding settings for the default rates? (The mmc/python2_encoding settings for the default rates are not in the properties file.)

- Andy

[DFA]

kny3twalker:

I am not having any particular trouble, just trying to pin down an answer on VBR vs. CBR. Obviously, higher / highest bit rate settings will yield better results (although diminshing). I do not care that if for slow action "Talk Show" material that I am wasting disk space (Sage has 500 Gig in my HTPC). Forget the "it depends on the subject matter" discussion. I'm not going to jump around with quality settings: I want the BEST all the time even if it's a 2 hour movie of grass growing and snails racing.

So is it VBR or CBR? I'm taking a guess that CBR is the better choice but have no technical reason for saying so.

DFA

[kny3twalker]

thats funny after being involved in SHS's forumk for so long
He would say different
From past posts as I remember
He always said the best quality is from a variable bit rate usually from 6 MB to 9 MB /sec

( I should really find a quote from him rather than trying to remember)

I can agree with that in all cases but sports

I like to do quality Max Quality 5.6 GB per hr Variable Rate
it just seems to do the best with sports and looks good with everything else
the only reason I choose lower bit rate recording is for cartoons
I know, but.........

there is just no reason to have a cartoon recording at that high of a bit rate and it saves space
but I will also say this I generally like recording qualities not that high for other subject matter cause it is does not get any better with the higher setting
but I still use very high quality recording bit rates in comparsion to some people I see here
basically I tried to do the best and DVD standard qualities for a while and was not happy with the resolutes well other than cartoons

I do like to do 6MB to 9 MB variable for most of my recording though
I just set the default a little higher to Max Quality 5.6 GB per hr Variable Rate(which is 9 to 12 MB/sec) just in case I watch sportscenter or for when football season comes around

so you can say that I am choosing more than one quality but really if space was no object then a VBR 12 MB/sec (9 MB to 12MB) would be my choice

[kny3twalker]

Opus4 you can do the math to find out that they are CBR rates as well
the best rate is 6666666 bit/sec that equals pretty much 3 GB/ hr

the way I know it before doing the math was by the old setup in version 1.4
where the separate little window poped up you could choose the default recording rate in sage then go into the popup window (where it had sharpness,audio, etc ) the bit rate was defined the same and they were all CBR
I never messed with the DVD qualities too much but I am assuiming they did the same thing
I also did not make custom qualities (variable rate for these)
but its cool
I know hauppauge were mostly VBR but sage liked CBR probably easier to figure out the recording rate
the only recording (per hour ) rate I added was the one for CBR highest quality

I will add this to FAQ, I was not sure if anyone could do that

also just remember that all recording rate are VBR in at least some ways
becuase even CBR does not do CBR perfect

I am going to wait until I do know for sure though that the defaults are CBR
I would hate to mislead people in the FAQ's and if I am wrong I will fix these recording qualities and make the add-ons CBR
but there was just too big of a gap between DVD standard/ BEST and Max 5.6 GB/hr