Ok, that makes sense. Thanks for the explanation!
The _expression_ could then be reduced to:
int cbr = s->maxbitrate - 16000;
but maybe that would be even more obfuscating :P
While we’re at it, I’m also wondering about the relationship
between (speex) quality and bitrate.
There are a number of quality levels in speex that require
different bitrates but it seems as if it’s quite possible to set a quality that’s
higher than the configured bitrate allows. Will speex then limit itself to the
available bitrate or will the quality level override this?
I suppose this question might be better answered by the speex
devel list but if anyone here knows the answer I’d love to hear it.
/Sven
From:
address@hidden
[mailto:address@hidden On
Behalf Of Vadim Lebedev
Sent: den 20 maj 2010 18:48
To: address@hidden
Subject: Re: [Linphone-developers] Question about speex
I'm trying to guess here
But 50 seems to be packets per second
so
maxbitrate/50 == bits per packet
bitsperpacket/8 == bytes per packet
IP header = 20 bytes, UDP header = 8 bytes, and RTP header =
12 bytes
bytes per packet - 40 == speex payload bytes per
packet
speex payload bytes per packet * 50 = speex
payload bytes per second
speex payload bytes per second * 8 == speex payload bits per
second
Seems correct?
Vadim
On 05/20/2010 03:19 PM, Sven Westergren wrote:
Hi,
Can someone explain to me the reasoning behind this recalculation of bitrate in the speex plugin (msspeex.c)?
/* convert from network bitrate to codec bitrate:*/
/* ((nbr/(50*8)) -20-12-8)*50*8*/
int cbr=(int)( ((((float)s->maxbitrate)/(50.0*8))-20-12-8)*50*8);
I have searched the speex manual but I can't grasp what is going on here.
Best regards
Sven Westergren
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