[speex-dev] Speex settings and jitter

John Hayes jhayes at thereinc.com
Tue May 20 11:12:07 PDT 2003

The audio frame speex generates sounds pretty terrible most of the time, and
I don't use it for jitter correction instead I just use it for dropped
packets - so I usually drop the late packet. It sounds acceptable as long as
I drop less than 5% of traffic (dropping 2 in a row makes a bad robot noise,
so I reset the stream in that case). The good news is that on an unsaturated
DSL line jitter and packet loss are basically 0.[1]

In my experience dropping a packet without decoding NULL or without playing
the gap packet make a really bad tick.


[1] The bad news is on a saturated DSL connection - it's basically unusable
without a second of jitter buffering.

> -----Original Message-----
> From: owner-speex-dev at xiph.org [mailto:owner-speex-dev at xiph.org]On
> Behalf Of Chris Flerackers
> Sent: Tuesday, May 20, 2003 9:05 AM
> To: speex-dev at xiph.org
> Subject: [speex-dev] Speex settings and jitter
> Hi,
> Is there are document where the interaction between all the configuration
> options of speex is explained?
> Speex seems to have CBR, VBR and ABR. You can also use SPEEX_SET_QUALITY
> (SPEEX_SET_VBR_QUALITY) and SPEEX_SET_BITRATE which I suppose can't be set
> at the same time. Is there a list of possible combinations somewhere?
> I also have another question related to jitter. To minimize jitter, you
> usually need to make the audio
> shorter and longer and preferably while keeping it sound smooth.
> What is the
> best way to do this
> with speex? I saw that you can pass NULL to the decode function
> to generate
> an audio frame which
> might be used to make the audio longer. Will speex always generate a
> "fluent" audio stream (without ticks, ...)
> when inserting these NULLs. And is dropping a packet a viable way to make
> the audio shorter?
> Best regards,
> Chris

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