Re: [rtcweb] Clarification on simulcast and RID and RepairedRtpStreamId

Sergio Garcia Murillo <> Tue, 04 December 2018 09:35 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 5A1B1130E78 for <>; Tue, 4 Dec 2018 01:35:30 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2
X-Spam-Status: No, score=-2 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (2048-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id eiiupX2D-6IR for <>; Tue, 4 Dec 2018 01:35:24 -0800 (PST)
Received: from ( [IPv6:2a00:1450:4864:20::32c]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 2E75D130E79 for <>; Tue, 4 Dec 2018 01:35:24 -0800 (PST)
Received: by with SMTP id z18so8797437wmc.4 for <>; Tue, 04 Dec 2018 01:35:24 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=L4D6BJ/f2ner4Dp1pDmcUVeEvSvNHeCUq+eCUOWFgDg=; b=Tk6gzdNeTumKEuQsxQxw6p2DwJW1rGRj/eoZAqSzWuAC3mi6sq2qhPdfCjUS742t/t 0gRm4oAAlDyIVICkk7VIIdq3KOtb+P9RbLCtXd1EQnT5hyyToRSSWlMblLCgUDzwkJFh a4s77gFPK2gARoN+f/xt78EMS47p2xXtA+g8og4F+jxj7o0HYLMb90pvHdCAZ0NfgjrZ NLAoldAsxx7LAmDCJ54yrlWhSedk/JWkHvhGBYwt1W9G9ca4BHBnTydYtuvLbThZXYEV 5vQPrkiLBdtgk71ReYCgMbY+9Y2w7vAn3hpsbADy+vYi6xqfwnDXhjRn8jy+3UPxwvqD l6ow==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=L4D6BJ/f2ner4Dp1pDmcUVeEvSvNHeCUq+eCUOWFgDg=; b=QZmlvPi6avuOdOOV/FsWnWmCFP1gmMRewMrhSXh9tELXTuYZxexyRXGJmkkG0sXq8D SR7pGswES89XhWKfMKnZzn9gjEo/OcSUnP+HKh3pY5uJB0gY8kmL10g/JrNIl35bEF6j buQaLeRLPkN2GGHQnUfvjm6G/GCnvpd5PpYtRzFfhKaCFLEdhr8ARo84/TWxLcyvg2Qg Kk7E02UfdznAU7V6eEYGc7OXOL682BdS6k25Vp3t9F+1sbFbJat8jAXMhLmlkyBk9UBF EZxWGJxn/8ZbPWrUx24mbnFvd3EsIG8l9k3DkczZE3DHRqsh1KH+RKfyczoo4gwyi2/Q fV/g==
X-Gm-Message-State: AA+aEWYi5nr3TOHXBCvdg65NJBGKgcpbN5e3P+yL3NLBzgjqD/cES/tX RN0HG4sPbuKzLbd1CFuIk+me+0H8
X-Google-Smtp-Source: AFSGD/UmiG3AG9Xvshpf2MxkGm9csLdjXWM0NRR8Obx3EJYVrDqqIHFxNDAEpggkDOFlgrrbTZaJZw==
X-Received: by 2002:a1c:c303:: with SMTP id t3mr10940824wmf.94.1543916122346; Tue, 04 Dec 2018 01:35:22 -0800 (PST)
Received: from [] ( []) by with ESMTPSA id e19sm38811044wrc.25.2018. (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 04 Dec 2018 01:35:21 -0800 (PST)
To: Iñaki Baz Castillo <>
Cc: Magnus Westerlund <>,
References: <> <> <> <> <> <> <> <>
From: Sergio Garcia Murillo <>
Message-ID: <>
Date: Tue, 04 Dec 2018 10:39:04 +0100
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.2
MIME-Version: 1.0
In-Reply-To: <>
Content-Type: text/plain; charset="utf-8"; format="flowed"
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Archived-At: <>
Subject: Re: [rtcweb] Clarification on simulcast and RID and RepairedRtpStreamId
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Real-Time Communication in WEB-browsers working group list <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Tue, 04 Dec 2018 09:35:31 -0000

On 03/12/2018 22:26, Iñaki Baz Castillo wrote:
> On Mon, 3 Dec 2018 at 22:22, Sergio Garcia Murillo
> <> wrote:
>> My point is that there is a single source in the transceiver/MID why
>> should we add default RID and waste 2 more bytes in each media and rtx
>> packet?
> Regardless what browsers do today, both MID and RID headers should be
> just included in the first packets. The receiver is supposed to update
> its ssrc table for faster matching.
> NOTE: The sender should also resend MID and RID if the SSRC changed
> because some RFCs state that SSRCs may conflict and things that
> absolutely never happen.
Kind of agree, but from a theoretical point of view remember that we 
introduced MIDs/RIDs to cover rtp proxing/switching scenarios in which 
ssrc conflicts may happen, so in order to cover those scenarios the 
MIDs/RIDs values must be included in every packet. If we ignore that, 
then could just go back to ssrc signaling and avoid mids/rids 
completely, which I would be in favor of.

Best regards