Re: [rtcweb] Video resolution SHOULDs (Re: resolutions in draft-cbran-rtcweb-codec-01)
Stephan Wenger <stewe@stewe.org> Thu, 17 November 2011 09:54 UTC
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Date: Thu, 17 Nov 2011 17:54:25 +0800
From: Stephan Wenger <stewe@stewe.org>
To: Harald Alvestrand <harald@alvestrand.no>, rtcweb@ietf.org
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Thread-Topic: [rtcweb] Video resolution SHOULDs (Re: resolutions in draft-cbran-rtcweb-codec-01)
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Subject: Re: [rtcweb] Video resolution SHOULDs (Re: resolutions in draft-cbran-rtcweb-codec-01)
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The highlighted part of Harald's suggestion below > SHOULD support resolutions of 1920x1080, 1280x720, 720x480, 1024x768, > > 800x600, 640x480, 640 x 360 , 320x240 *if these resolutions can be > displayed on the target device* > seems sensible. However, I have another issue. I don't believe that naming specific resolutions is advisable. In a system where the rendering side has almost undefined picture properties because they are typically rendered in "windows", it IMO does not make much sense to limit yourself to certain aspect ratios, picture sizes etc., even if those correspond to today's preferred sensor resolutions (or integer fractions thereof). Resampling an input signal is cheap nowadays (at least compared to the encoding itself), and cropping is even cheaper. I would instead recommend naming one single MUST resolution (as the draft does) to ensure minimum interoperability, and otherwise negotiate a processing rate in macro blocks per second (or equivalent), with fixed constraints around the aspect ratio. Just as what H.264 does in its level specification. In fact, if H>264 turns out to be our mandatory codec, then I would adopt the level spec wholesale. As for said mandatory resolution, I believe that 320x240 is sooo yesterday. Even on something like an iPhone, you can do better today. Who uses 4:3 ratio nowadays? My vote would go towards something like WQVGA or even WVGA. Stephan From: Harald Alvestrand <harald@alvestrand.no> Date: Thu, 17 Nov 2011 16:50:54 +0800 To: <rtcweb@ietf.org> Subject: [rtcweb] Video resolution SHOULDs (Re: resolutions in draft-cbran-rtcweb-codec-01) On 11/17/2011 11:19 AM, Roni Even wrote: > > > > Hi, > > The text in the draft on video codec is > > > > o MUST support a minimum resolution of 320X240 > > > > o SHOULD support resolutions of 1280x720, 720x480, 1024x768, > > 800x600, 640x480, 640 x 360 , 320x240 > > > > I propose adding 1920 x 1080 to the SHOULD. This resolution are used by video > conferencing systems > > I think I want to object to making this a SHOULD, but it's possible we just don't understand the requirement the same way.... The RFC 2119 SHOULD definition says: 3. SHOULD This word, or the adjective "RECOMMENDED", mean that there may exist valid reasons in particular circumstances to ignore a particular item, but the full implications must be understood and carefully weighed before choosing a different course. When designing an RTCWEB implementation for my mobile phone, with its (comparatively) microscopic screen and anemic processor and battery, it takes approximately zero seconds to decide that I won't waste energy (literally) on decoding HD; I'll make sure I negotiate down to something more sane for me if someone's unkind enough to suggest it to me. I would be happy to write the requirement as SHOULD support resolutions of 1920x1080, 1280x720, 720x480, 1024x768, 800x600, 640x480, 640 x 360 , 320x240 if these resolutions can be displayed on the target device but I would not be happy to just extend the requirement as it is proposed today. (Yes, I know, this means that I've turned down-negotiation of video resolution into a MUST. I think it already is, but I think we haven't talked explicitly about it.) > > > > > > > > > I also assume that there will be a way to negotiate the video parameters (no > issue if we use offer/ answer RFC 3264) > > > > Roni Even > > > > > > > > > > _______________________________________________ > rtcweb mailing list > rtcweb@ietf.orghttps://www.ietf.org/mailman/listinfo/rtcweb > _______________________________________________ rtcweb mailing list rtcweb@ietf.org https://www.ietf.org/mailman/listinfo/rtcweb
- [rtcweb] resolutions in draft-cbran-rtcweb-codec-… Roni Even
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… Roni Even
- Re: [rtcweb] resolutions in draft-cbran-rtcweb-co… Cary Bran (Standards Mailer)
- [rtcweb] Video resolution SHOULDs (Re: resolution… Harald Alvestrand
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… Stephan Wenger
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… Harald Alvestrand
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… Roni Even
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… James M. Polk
- Re: [rtcweb] resolutions in draft-cbran-rtcweb-co… Aron Rosenberg
- Re: [rtcweb] resolutions in draft-cbran-rtcweb-co… Ralph Giles
- Re: [rtcweb] resolutions in draft-cbran-rtcweb-co… James M. Polk
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… Ralph Giles
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… Harald Alvestrand
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… Harald Alvestrand
- Re: [rtcweb] resolutions in draft-cbran-rtcweb-co… Bran, Cary
- Re: [rtcweb] resolutions in draft-cbran-rtcweb-co… Bran, Cary
- Re: [rtcweb] resolutions in draft-cbran-rtcweb-co… Ralph Giles
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… Bran, Cary
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… Ralph Giles
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… James M. Polk
- [rtcweb] Interlace (Re: Video resolution SHOULDs … Harald Alvestrand
- Re: [rtcweb] Interlace (Re: Video resolution SHOU… Stephen Botzko
- Re: [rtcweb] Interlace (Re: Video resolution SHOU… Ralph Giles
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… Ralph Giles
- Re: [rtcweb] Video resolution SHOULDs (Re: resolu… Stephen Botzko