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From: | Gunnar Hellström |
Subject: | Re: [Linphone-developers] Video quality control system on linphone (with fallback to audio) |
Date: | Sun, 21 Oct 2012 21:41:21 +0200 |
User-agent: | Mozilla/5.0 (Windows NT 6.1; WOW64; rv:16.0) Gecko/20121010 Thunderbird/16.0.1 |
Ivan,
Part of what you ask for is available in Linphone. In RFC 3550, RTP, there are defined periodic reports through the RTCP transmissions. The proposed frequency of these reports is one per a few seconds, e.g. 5 seconds. The contents of the RTCP RR Receiver Reports is supposed to contain a number of fields for feedback from receiver to transmitter. Among these fields are fields for reporting packet loss, and jitter. However, I have not seen this part of the RTCP reports from Linphone. So, for making use of this reporting for Linphone, I see two actions required: 1. Add at least packet loss info and possibly more quality related RTCP fields to the RTCP RR reports. 2. Add evaluation logic of the RTCP RR reports for video, and introduce as a first action when bad transmission is reported, to reduce target bandwidth, reduce resolution to QCIF and increase Quantization. Only if that is not sufficient, you may optionally turn off video, but that should be on agreement with the user. Maybe you can select a more narrow band audio codec instead. A video stream even at low resolution may say more than 1000 words. Remember to also have a smooth algorithm for trying to regain bandwidth and quality when networks seem better, but be careful to not enter wild feedback fluctuations in these changes. It is also good to include an option to use text, e.g. real-time text as a complement that usually goes through even in terrible network conditions. Maybe the Linphone team already has something in this direction planned or developed? Regards Gunnar ------------------------------------------------------------------------- On 2012-10-19 15:03, IVAN FERNANDEZ wrote:
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