- From: Stefan Håkansson LK <stefan.lk.hakansson@ericsson.com>
- Date: Thu, 5 Oct 2017 10:12:24 +0000
- To: "Cullen Jennings (fluffy)" <fluffy@cisco.com>
- CC: WebRTC WG <public-webrtc@w3.org>
On 02/10/17 18:44, Stefan Håkansson LK wrote: > On 02/10/17 18:30, Cullen Jennings (fluffy) wrote: >> >>> On Sep 26, 2017, at 5:56 AM, Stefan Håkansson LK >>> <stefan.lk.hakansson@ericsson.com <mailto:stefan.lk.hakansson@ericsson.com>> >>> wrote: >>> >>> Therefore I propose we remove the current text on 'centering, scaling, >>> cropping', and instead reference JSEP section 3.6.2. >> >> That is what we originally had and Martin and others complained that more advice >> was needed. I don't think we can change the current advice but it still seems we >> need to say something to have consistent behaviour between browsers. I do think >> consistent behaviour is important because removing this going to result in >> letter boxing and when one thing does it one way and something else does it >> another, you can end up with the situation with a black border all the way >> around the outside of image. Apps will need to know what the browser are going >> to do so that the application can compensate to achieve the desired outcome for >> the application. >> >> I think EKR and Justin have argued for one of the principals being don't loose >> information by cropping as this is really bad in cases like screen share. They >> are also arguing for don't change aspect ration (other than minor bit caused by >> rounding error in scaling ). So I think that means this needs to say something >> along the lines of black border is added to image to get to correct aspect >> ratio, then it is scaled to get to correct size. > > Part of my reasoning is that the sender side does not (usually) know the > rendering size on the remote end. All the sender knows is what the > receiver is able to receive/decode, it does not know the rendering > dimensions so it would be impossible to know if there would be a black > border anywhere when this is eventually rendered. "Correct" size is > unknown as I have understood it. I added a note trying to explain that letterheading/pillarheading is the result if the track aspec ratio is different from the video element aspect ratio (regardless of whether video has been rescaled or not): https://github.com/w3c/webrtc-pc/pull/1570/commits/b7cab1df0df8a7c05459dc0079b94662a2bde2e9
Received on Thursday, 5 October 2017 10:12:50 UTC