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Old 04-03-2010, 01:56 PM   #1
cosmotic
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Default Speex Codec bitrate

It seems the general consensus is that the Speex codec is better than GSM. That may be true when comparing sound for the same bitrate, however the GSM codec options in Ventrilo have a much higher maximum bitrate than the maximum bitrate available for Speex. The admins of the server I use (which is set to the highest quality GSM codec) don't want to change the server-wide codec to Speex because it 'sounds worse than GSM'.

The maximum bitrate for Speex should be increased to be in-line with GSM. If that means a bitrate that is still lower but with an audio quality similar to the highest GSM quality, that's fine, but bitrate equal to the highest GSM yielding a higher quality sound would be ideal.

Additionally, It would be great to have an 'ignore codec errors' option so I don't get errors every time I log in (lobby is set to server default, GSM) or get sent to the idle channel (set to server default, GSM).

I tried changing the default channel in the server properties but it isn't working, even when I use the copied channel name "The Plantation"... I tried without the space and it still doesn't work. Any ideas?

-Charlie
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Old 04-06-2010, 01:41 PM   #2
mjgraf
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ask the server admin to set a default channel for your user in the user editor. The server will override your local client default channel.
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Old 04-07-2010, 01:33 PM   #3
Jaycyn
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Spexx > GSM.

Tell your Vent Admin that while GSM does have a 'higher bit rate' that does not necessarily translate to any real world improvement. It's like your cable modem - yeah it's rated at 10M per second but real world you actually get 7.

He should try the Speex codec at the following settings (from Mac Troubeshooting, step #3)

There are dozens of different settings for Speex codecs, and a lot of getting the best one for your server is trial and error. However, Speex 16 KHz, 16 bit, 10 Qlty is a good starting point - if vent users experience lag or dropouts lower the setting to 5 Qlty, and try it. Then lower it to 8 bit etc etc

Speex is more efficient that GSM (imo) so it doesn't have to work as hard to get the same sound quality.
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Old 04-10-2010, 05:38 PM   #4
cosmotic
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Jaycyn:

I think you misunderstand. Compare the sound quality of the highest setting for both GSM and Speex. GSM (at its highest available bitrate in vent) sounds better than Speex (at its highest available bitrate in vent). The admin refuses to change the default codec because its currently set to the best sounding codec, GSM (at its highest available bitrate in vent).
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Old 04-13-2010, 04:05 AM   #5
cosmotic
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The codecs that Ventrilo uses no doubt take parameters to produce the final output. Among these parameters are ones used to control the bitrate of the resulting encoded audio stream.

To facilitate the configuration of the codecs, Ventrilo presents the user with a series of presets. These presets are a set of pre-configured parameters that the codecs will accept, but not an exhaustive set of all possible configurations of parameters.

Ignoring all but the highest-bitrate, and highest quality audio accordingly, we have:
GSM 44KHz, 16bit: 8905 Bytes per second
Speex 32KHz, 16 bit, 10 Qlty: 5520 Bytes per second

Of these two possible settings, GSM produces a superior-sounding audio stream, albeit at a much higher bit rate.

However, I'm fairly certain that Flagship has chosen a maximum Speex preset that is well below that which COULD be used. Speex documentation lists bit rate as one of the parameters that can be used and mentions no maximum bit rate. Flagship should patch Ventrilo to allow Speex codec configurations that result in higher bit rate (and thus higher quality) encoded audio streams.
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Old 04-14-2010, 01:49 PM   #6
Jaycyn
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Out of curiosity, are you assuming that GSM sounds better than Speex at that bit rate? Or have you actually worked with them both at that bit rate (I have).

If that's an assumption (which is a logical one), it's like saying that USB 2.0 (480M) is faster than FireWire 400 (400M) because it has a bigger number (480M > 400M).

There is quite a bit more too it than that as, all of us Mac users know, Firewire smokes USB in real-world performance.

Speex was optimized and designed to run at 8Khz, 16Khz, and 32Khz and performs best at those rates for internet communications.

Running a codec at a higher setting than is necessary may also cause other issues as you are using a gob of unnecessary bandwidth which may have other implications (like WoW Laaaaag). I always recommend selecting a bandwidth where the communication is clear and without any interference - anything more is (in general) a waste.

Speex also has a quality parameter (1-10) which can give you additional control of quality levels, which is why Speex can run at a lower Khz and achieve similar quality to GSM in real-world applications. You can trade out quality for bit rate which other codecs like GSM don't offer.

The other cool thing about Speex is that it is (imo) much more intelligent in how it handles encoding. It uses varible bit rates to match to the type of sound it's encoding. I don't believe GSM currently supports that - I think it's 'flat' i.e. everything encodes the same.

Last edited by Jaycyn; 04-14-2010 at 02:02 PM.
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