Re: [rtcweb] Fwd: Last Call: <draft-ietf-rtcweb-audio-10.txt> (WebRTC Audio Codec and Processing Requirements) to Proposed Standard

[Roman Shpount <[e-mail]>]

On Thu, Mar 3, 2016 at 6:49 AM, Harald Alvestrand <[e-mail]>
wrote:

> You've made this argument before. I cannot see that anything new has
> been brought to the table that is likely to alter the WEBRTC WG
> consensus to have these enforced limits.
>

Am I correct to understand that WEBRTC WG decided that there should be
limits on DTMF tone generation and it is up to this group (IETF rtcweb) to
decide the exact values of these limits?

In this case, as I have stated before, the maximum tone duration should be
8000 ms to match possible tone duration for RFC 2833 DTMF tone. RFC 2833
was in use for the past 15 years and no one reported any issues with this
limit.

Minimum tone duration of 40 ms and minimum gap duration of 30 ms are
minimum physically required to transmit DTMF tone as 8 KHz audio signal and
still satisfy the talk-off specifications. These limitations have not
caused any practical issues for the past 50 years. I would like to mention
that shorter tones are used during call setup since it can be guaranteed
that no audio signal is present and talk-off requirements are relaxed.
Furthermore VoIP only networks, which use RFC 2833/RFC 4733 tones, can
support tones and gaps of anything from 0 ms and up. This is why I
initially advocated for 0 ms min duration. On the other hand if the group
decides that removing one more potential foot gun is more important, I will
not be too upset.

If anybody can come up with the practical example where tones longer then 8
sec or shorter then 40 ms with less then 30 ms gaps are used, please report
them to the list. Otherwise, let's document what is in W3C TR and move on.

Regards,
_____________
Roman Shpount