"Quality Control" settings (2 Viewers)

[Keneo]

There does not seem to be any documentation for the "Quality Control" tab in the TV server app.
The wiki only contains screen shots of this tab. No explanation.

I think I understand what the Recording radio buttons will accomplish.
But I can't imagine what the Playback ones do.

Also, I managed to find out what Variable Bit Rate vs. Constant Bit Rate do.
But what is the difference between VBR "peak" and VBR "average" ?

Finally, what are the Custom Settings for?
Do they only take effect when the Custom radio button is selected?
Or are they related to the Bitrate Mode settings?

 

[misterd]

I will try to explain those settings.
TvServer can have two settings for qualtiy. One which is used for recordings and one for normal playback/timeshifting/watching Tv. While watching Tv you can change those settings temporarily via the context menu in MP. Also you can overwrite the settings for scheduled recordings within MP.

A quality settings consist of two parameters:
- Bitrate mode
- Bitrate

This means only the combination of the selected bitrate mode and bitrate defines the whole quality that is used.

TvServer uses a standardized interface which supports three bitrate modes:
- Constant bitrate: The bitrate is constant all the time. As bitrate the selected value will be used.
- Variable bitrate (Average): The bitrate that is used is variable, but in a specific time period (normally 5 minutes) the bitrate is the selected one.
- Variable bitrate (Peak): It is the same like Variable bitrate (Average) except that the maximum (peak) bitrate is also defined.

Unfortunately there exists not a standardized range for the bitrate. Therefor TvServer uses percental values. The values are:
- Default: The default bitrate of the encoder, including the default peak bitrate of the encoder.
- Portable: Minimum bitrate + 20% of the available range as standard bitrate. For the peak value 45% will be added.
- Low: Minimum bitrate + 33% of the available range as standard bitrate. For the peak value 55% will be added.
- Medium: Minimum bitrate + 66% of the available range as standard bitrate. For the peak value 80% will be added.
- High: Minimum bitrate + 100% of the available range as standard bitrate. For the peak value also 100% will be added.
- Custom: In this case the minimum bitrate plus the defined custom values in this tab ("Custom settings")

Sometimes the used encoders doesn't report the really possible maximum bitrate through the standardized interface. This means that TvServer isn't able to use the maximum quality a the encoder doesn't report the correct values.

MisterD

 

[Keneo]

Misterd,
Thank you very much for your explanation.
You have helped me understand these settings a little better.

Let me see if I understand correctly...

(1) You are saying that the "Custom Settings" percent values are only used when the Bit Rate is set to "Custom"
(2) Both VBR peak and VBR average have a bitrate maximum defined by the Bitrate selection. For both VBR peak and VBR average there is a time period to reach the maximum.
(3) In the custom settings, if Value is set to 50% this means that the encoder will use 50% of the remaining available bandwidth of the card.

Can you tell me what the "peak" value is used for?

My goal is to record with maximum possible quality and I do not care about how big the file becomes.
I have set bitrate to "High" but which Bitrate Mode should I use?

Thanks again for your help.

You seem very knowledgeable about this. Maybe you should edit the wiki?

 

[Spragleknas]

First: Thanks for answering, MrD

I'll try to get this into the wiki, as I said, but I would like to take the opportunity to say that
EVERYONE CAN HELP IMPROVE THE DOCUMENTATION OF MP BY ADDING STUFF LIKE THIS TO THE WIKI

 

[geov]

Thanks MisterD....at last someone explains it....

So if I selected....

1) Constant bit rate mode
2) Custom Bit Rate
3) Value = 100%

Does that give me the best possible setting "all the time"?

 

[misterd]

I will try to explain it with an example. Let's assume that the used encoder reports a minimum bitrate of 3000 kBit/s and a maximum bitrate of 80000 kBit/s.

Now we assume that you have entered 50% and 75% as the custom values. Than the encoder will use the following bitrates, if you choose "Custom" in the bitrate option:
- Constant bitrate: 5500 kBit/s (3000 + (0,5 * 5000)) all the time
- Variable bitrate (average): The encoder will use a bitrate between 3000 kBit/s and 8000 kBit/s, but in a specific timeperiod (normally 5 minutes) the average bitrate is 5500 kBit/s (3000 + (0,5 * 5000))
- Variable bitrate (Peak): The encoder will use a bitrate between 3000 kBit/s and 6750 kBit/s (3000 + (0,75*5000), but still in a specific timeperiod the average bitrate is 5500 kBit/s (3000 + (0,5 * 5000))

If you choose other options for the bitrate, than the encoder will use the values which I explained in the last post. The custom option should only give the users the possibility to use a own value.

The Peak value defines as you can see in the example the maximum bitrate that the encoder will use in the desired mode.

Unfortunately an encoder has the possibility to support different ranges for the different encoding modes. This means that for Constant bitrate the range could be 3000-8000 kBit/s like in the example, but for the two variable bitrate modes the range is 5000-10000 kBit/s.

Generally if you want the best quality you should just set the bitrate to "High" as this is identical to 100% in the custom values. As described above the maximum bitrate can be different, so you have to try unfortunately.

I know that this isn't the best solution, but at the moment we don't know which encoder will be used when the recording starts. The reason is that the encoder is not stored in our configuration file. For HW-encoding cards normally TvServer will use always the same encoder, but for SW-encoding cards the encoder can change everytime as it depends on the installed encoders.

MisterD

 

[Keneo]

Do these settings apply to audio encoding as well? I am currently not happy with the sound quality of my hauppauge and was hoping this would resolve it. Is there another away to adjust sound ?

 

[misterd]

Currently those settings apply only the video encoder and I can't say if and when such an extension will be added to TvServer.

MisterD

 

[gserg]

I can't get to Quality Settings, it is greyed out and unavailable. Do you know why this is not an option for me? I am using 1.0.2.

Thanks for any help or guidance.

 

[Spragleknas]

Depends on TV-vard, so...