Re: [AVTCORE] What does "same codec+configuration" mean?

Iñaki Baz Castillo <> Tue, 22 March 2016 16:15 UTC

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From: =?UTF-8?Q?I=C3=B1aki_Baz_Castillo?= <>
Date: Tue, 22 Mar 2016 17:13:39 +0100
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To: Magnus Westerlund <>
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Subject: Re: [AVTCORE] What does "same codec+configuration" mean?
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2016-03-22 15:55 GMT+01:00 Magnus Westerlund <>om>:
> So if one reads the bundle specification it says the following:
> 10.1.2.  Payload Type (PT) Value Reuse
>    Multiple bundled "m=" lines might represent RTP based media.  As all
>    RTP based media associated with a BUNDLE group belong to the same RTP
>    session, in order for a given payload type value to be used inside
>    more than one bundled "m=" line, all codecs associated with the
>    payload type number MUST share an identical codec configuration.
>    This means that the codecs MUST share the same media type, encoding
>    name, clock rate and any parameter that can affect the codec
>    configuration and packetization.
>    [I-D.ietf-mmusic-sdp-mux-attributes] lists SDP attributes, whose
>    attribute values must be identical for all codecs that use the same
>    payload type value.
> So identical a=rtpmap and a=fmtp lines would meet this criteria.
> However, two different m= blocks configuring a particular PT for a codec
> could possibly use different values for an optional parameter that can be
> received correctly by either configurations.
> Codecs that can produce different encoding bit-rates can in many cases be
> used at different bit-rates and fulfil this requirement.
> The underlying issue is that what is identical codec configurations are
> codec specific. Thus hard to write a precise definition of it.
> Does this help?

It helps, and I'm sorry since I missed the above text in BUNDLE spec.

Thanks a lot.

Iñaki Baz Castillo