Hello, My name is Robin Mar?n and I have some questions about the Theora Codec/project... First of all I don't know if this is the right place to ask but I haven't found any Xiph/Theora forum or something similar... I don't even know if this is the right way of "posting" in mailists... But anyway... I discovered Theora just like a moth ago when the 1st alpha of Thusnelda came out... Even when just a month ago I found about it, I did a lot of reading and searching to know more about the concept, goals and some basic internal working of Theora. Of course, I did a lot of testing with the 1st Thusnelda alpha of ffmpeg2theora and results are very good! I'm very pleased with results. Compression, quality, ease of use and stability are really great even when there's a good amount of new code since Theora 1.0 version (for what i've read). Congratulations to the devs! Even so, In most cases I can still get better quality with Codecs like Xvid using a Two-Pass setup... So here's the first row of questions: *- Is it possible to support a "Two-Pass" or even "multipass" feature in Theora? *- Is there any plan to support that or a similar feature in Theora? ... And just to clarify, I'm not asking for timeframes, just if it's possible... if it's in the plans... of is there's a similar feature on the "roadmap" :) Ok, and the other questions relates to the future of Theora against modern codecs like the frequently mentioned h264 stuff... And please, don't get me wrong, I'm just wondering if there are plans to support more advanced features even if that supposes rising the CPU load or stuff like that... Concretely my questions are: - knowing that your "goal" with Theora is/was (?) to achieve similar quality than MPEG-4 Part-2/ASP (?) - *- Do you plan to implement more advanced features comparable with MPEG-4 Part-10/AVC? (h264) And more than that... *- Can you implement such comparable features in current Theora/Thusnelda or that would require a whole new direction? Please notice I wrote "comparable"... not the same. I understand Theora is a different implementation. The last question is the most important for me... I'm very curious about that. Thanks tuqueque. -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.xiph.org/pipermail/theora/attachments/20090426/6d27f409/attachment.htm
On Sun, Apr 26, 2009 at 3:40 PM, ertuqueque <ertuqueque at gmail.com> wrote: [snip]> *- Is it possible to support a "Two-Pass" or even "multipass" feature in > Theora?It's possible in any variable bitrate codec.> *- Is there any plan to support that or a similar feature in Theora?It's certainly something that would be nice to have, it just simply hasn't been a high priority. You can achieve the same (or better) effect as a two pass encode by encoding with the quality knob and iteratively adjusting it until you get the desired total size. The downsize of this is that you'd have to do it manually and it can take up to 6 passes to find the right value. [snip]> Ok, and the other questions relates to the future of Theora against modern > codecs like the frequently mentioned h264 stuff... > And please, don't get me wrong, I'm just wondering if there are plans to > support more advanced features even if that supposes > rising the CPU load or stuff like that... Concretely my questions are: > > - knowing that your "goal" with Theora is/was (?) to achieve similar quality > than MPEG-4 Part-2/ASP (?) - > > *- Do you plan to implement more advanced features comparable with MPEG-4 > Part-10/AVC? (h264)This really sounds like you're asking for a buzzword comparison. There are a lot of buzzwords associated with these formats that people like to throw around. "Oh yea, well my coded has a 500cc hemi and dual cryo-cooled turbo-chargers!". Buzzwords are marketing. We could use some better marketing for Theora, but I suspect you want an engineering answer and buzzwords have no place in engineering. I'm no MPEG-4 part 10 expert, but I can at least list a couple obvious differences between -2 and -10. * Deblocking in the coding loop. Theora already does this. * Quarter-pixel MVs. Theora already does this. * 4:2:2, and 4:4:4 chroma formats. Theora format supports it, it should be in 1.1 * Data partitioning. Theora's encoding order is naturally suited to unequal protection. (The whole frame coefficient interleave) * encoder selected custom quant matrices (Theora format supports that, should be used in 1.1) Most of the other enhancements in part-10 over part-2 are not possible in Theora without breaking the bitstream (i.e. the better (arithmetic) entropy coding, variable MV and DCT partition sizes), violating patents, or are simply inapplicable to Theora (increase flexibility in b-frame modes? Theora has no b-frames).
I'll also answer, which is not meant to imply that Gregory's answers were somehow lacking :-)> First of all I don't know if this is the right place to ask but I haven't > found any Xiph/Theora forum or something similar...Within the company we don't use a forum because it's useful for chatting, but not really for getting work done. It might be useful for user support, but we don't really have the resources to offer such a thing on a continuous basis. We do help folks who pop into IRC or ask questions on the mailing list. For general codec discussions, there are already other good places to go to, eg, HydrogenAudio for audio and doom9 for video.> I don't even know if this is the right way of "posting" in mailists... But > anyway...Yep. You send mail. Pretty simple :-)> Of course, I did a lot of testing with the 1st Thusnelda alpha of > ffmpeg2theora and results are very good! I'm very pleased with results. > Compression, quality, ease of use and stability are really great even when > there's a good amount of new code since Theora 1.0 version (for what i've > read). > Congratulations to the devs!I'm glad you've had good results. In general the tools have a long way to go.> *- Is it possible to support a "Two-Pass" or even "multipass" feature in > Theora?Yes.> *- Is there any plan to support that or a similar feature in Theora?Originally I hadn't considered two-pass to be all that compelling. The biggest reason you're getting better results using two pass in Xvid is because, right now, xvid is still a better codec (not surprising, Thusnelda is not finished. There's still a major piece of infrastructure missing in the encoder). That said, two pass makes some interesting optimizations useful and we may well implement a two-pass mode in our own encoders.> - knowing that your "goal" with Theora is/was (?) to achieve similar quality > than MPEG-4 Part-2/ASP (?) -We will keep up for a period. On paper, MPEG part 2 and part 10 are considerably more advanced codecs. However, a codec's quality performance is only as good as the encoder, and we've got alot of room for improvement yet (as does MPEG of course). Eventually, MPEG4 will surpass Theora for good, but we'll probably still have comparative lightweightness working for us.> *- Do you plan to implement more advanced features comparable with MPEG-4 > Part-10/AVC? (h264)If not in Theora than in a successor. The only disagreement within the org is which of those two paths to take. I'd like to modestly extend Theora, and Time would like to start fresh.> And more than that... > > *- Can you implement such comparable features in current Theora/Thusnelda or > that would require a whole new direction?Well it depends what you mean. There are features within theora we don't yet use or use efficiently. They wouldn't really be new. Eg, two pass would not require anything new, just a different way of using what we already have. If you mean 'new features' in terms of improvments to the format itself, then you're talking about changes that are extensions by definition. Monty