Re: [rtcweb] VP8 / H.264 conversion without transcoding
Justin Uberti <juberti@google.com> Thu, 21 November 2013 20:25 UTC
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From: Justin Uberti <juberti@google.com>
Date: Thu, 21 Nov 2013 12:25:27 -0800
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To: Gili <cowwoc@bbs.darktech.org>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] VP8 / H.264 conversion without transcoding
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Even if we could do this conversion in real-time on a mobile device... since you have both codecs present, why not just send the desired format in the first place? On Thu, Nov 21, 2013 at 11:25 AM, Gili <cowwoc@bbs.darktech.org> wrote: > Cullen, > > Thanks for the background information. I also remember them saying that we > are only at the beginning of this process and that they expect more > performance improvements in the upcoming months. > > It would be nice to gauge how far we are from being able to do this kind > of conversion in real-time on a mobile device (I suspect very far, but it's > worth asking). This has implications for P2P interoperability between VP8 > and H.264 peers without a middleman. > > Gili > > > On 21/11/2013 10:46 AM, Cullen Jennings wrote: > >> It's a cool demo and I talked to the team that did it. This is only >> possible because VP8 and H.264 are very similar codecs. The idea is to not >> redo the motion vector computations or the DCT but just reuse the values >> from one format in the other since they are the same. They hope that this >> can provide reduce the CPU by 1/3 from a full decode then re-encode. It >> also help reduce loss of quality for video. Other people have talked about >> this idea over the years and many people think it can give a 2 to 3 speed >> up so that seems consistent with their goals. >> >> It still requires the same bandwidth, and has similar other impacts. I >> can not see any way that it would not require MPEG-LA IPR for 264. >> >> >> On Nov 21, 2013, at 6:27 AM, Mo Zanaty (mzanaty) <mzanaty@cisco.com> >> wrote: >> >> This probably refers to an intelligent transcoder versus a brute force >>> transcoder. An intelligent transcoder harvests more data during decoding >>> than just the raw output pixels, and uses this extra data to ease encoding. >>> Data like block partitions, motion vectors, intra modes, quantization >>> parameters, etc. >>> >>> This is common for common conversions, like MPEG2 to H.264. VP8 and >>> H.264 are much closer formats, so this can significantly improve transcoder >>> performance. >>> >>> However, this is strictly a performance optimization, with no impact on >>> IPR or licensing issues. >>> >>> Mo >>> >>> >>> On Nov 21, 2013, at 2:51 AM, "Bossiel" <bossiel@yahoo.fr> wrote: >>> >>> This could be true if they can also walk on water and change it into >>> wine. >>> To be serious, no it's not possible. >>> Mamadou >>> >>> Sent from my iPhone >>> >>> On Nov 21, 2013, at 3:13, Gili <cowwoc@bbs.darktech.org> wrote: >>> >>> Hi, >>>> >>>> I'm at the WebRTC World conference. If I understood correctly, Zingaya >>>> just demoed what they claim is a VP8 to H.264 bridge that converts the >>>> video without transcoding. My interpretation is that they convert the >>>> surrounding packet format without re-encoding the actual video. Someone who >>>> understands codec internals (I don't) might want to validate this claim, >>>> because it could have a significant impact on the MTI debate. >>>> >>>> It sounds far fetched, but imagine the possibilities: >>>> • If the video is not being re-encoded, do H.264 royalties >>>> apply? >>>> • If the conversion is really cheap, is it feasible to connect >>>> a H.264 peer to a VP8 peer and have one of them convert in-line (no MCU)? >>>> Gili >>>> _______________________________________________ >>>> rtcweb mailing list >>>> rtcweb@ietf.org >>>> https://www.ietf.org/mailman/listinfo/rtcweb >>>> >>> _______________________________________________ >>> rtcweb mailing list >>> rtcweb@ietf.org >>> https://www.ietf.org/mailman/listinfo/rtcweb >>> _______________________________________________ >>> rtcweb mailing list >>> rtcweb@ietf.org >>> https://www.ietf.org/mailman/listinfo/rtcweb >>> >> _______________________________________________ >> rtcweb mailing list >> rtcweb@ietf.org >> https://www.ietf.org/mailman/listinfo/rtcweb >> > > _______________________________________________ > rtcweb mailing list > rtcweb@ietf.org > https://www.ietf.org/mailman/listinfo/rtcweb >
- [rtcweb] VP8 / H.264 conversion without transcodi… Gili
- Re: [rtcweb] VP8 / H.264 conversion without trans… Bossiel
- Re: [rtcweb] VP8 / H.264 conversion without trans… Mo Zanaty (mzanaty)
- Re: [rtcweb] VP8 / H.264 conversion without trans… Cullen Jennings
- Re: [rtcweb] VP8 / H.264 conversion without trans… Mohammed Raad
- Re: [rtcweb] VP8 / H.264 conversion without trans… Gili
- Re: [rtcweb] VP8 / H.264 conversion without trans… Cullen Jennings
- Re: [rtcweb] VP8 / H.264 conversion without trans… Bossiel
- Re: [rtcweb] VP8 / H.264 conversion without trans… Monty Montgomery
- Re: [rtcweb] VP8 / H.264 conversion without trans… Stefan Slivinski
- Re: [rtcweb] VP8 / H.264 conversion without trans… Justin Uberti
- Re: [rtcweb] VP8 / H.264 conversion without trans… Mohammed Raad