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13th June 2003, 01:01 | #1 | Link |
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A word on DivX / XviD capable DVD Players
Doom9,
I saw your home page post today about that MPEG-4 hardware player you bought and think it really shows why we think its important for hardware manufacturers or consumer electronic manufacturers to work with us (DivX) to ensure that content actually plays back well on devices. Unfortunately there are a few companies who don't seem to understand or care about high quality, stability and performance. It really irritates me that many of these companies are marketing how their devices play DivX or XviD content well and this is just not the case. Because we (DivX) knew this would happen we created our certificaton program to try and prevent companies from trying to confuse and misinform users into believing they are getting a DivX player. We decided we had to make sure these devices work the way they should otherwise users would have a horrible experience. People keep asking why devices haven't come out sooner supporting DivX and this is why, we don't want them to unless it works the way we as users would expect it to! And the good thing is we have quite a few partners very close to full certification. KISS-Technology as a partner is a great example. They understand how important it is to ensure their product performs very well and as they would expect it to if they spent the cash on it. Stayed tuned for quite a few more in the coming months. A few things on why these companies are experiencing problems. These companies are use to creating cheap MP1\VCD, and MP2 Players that can't deal with data rate spikes you see in DivX from using Variable Bit Rate. They can't afford the memory required to handle this influx of data during peaks (overflows the memory bucket) and this and weak processors are the cause for most of these problems. It's combination of weak hardware and little memory yet they don't seem to care that they are selling these devices emphasizing DivX and XviD playback as a key feature when in fact the experience is horrible. That's why on DivX 5.0.4 we created the new Rate Control Algorithm which has something called VBV (Video Buffer Verifier). This ensures that data can still have spikes but in a way that will not create problems on hardware. VBV defines the memory size. For each hardware manufacturer working with us they must be able to handle content within this VBV range ++. This ensures they can handle the memory. We of course also verify performance (frame rate) and most importantly that quality is acceptable. This is a challenged since even though our partners use the authentic DivX Hardware SDK's we created they still have to build hardware so that it can handle the performance required for playback (fast hardware with enough memory). So regardless of who the partner is we don't allow our name to be used on the box stating DivX Compatible or Certified unless they meet these requirements. Of course companies will say plays DivX or XviD but unless you see our ugly stamp saying certified then I would caution trusting it. I think many people haven't understood the importance of why we created a DivX Certification program. This is exactly why we did this. We knew this would happen. This ensures that when a DivX user user see's an authentic DivX Certification logo on a product they would know that we in fact certfied the product in being able to handle DivX content. If it doesn't have it then I can't comment on its ability to be a good reliable product. If it can't handle DivX it can't handle XviD or possibly many other flavors of MP4 codecs. It's unfortunate there are companies doing this as I'm sure plenty of people are going to be spending money on devices that can't do what they expected them to do when they payed for them. So please make sure either you get good honest feedback on a product claiming it can playback DivX or XviD and of course if it has our Certification Logo you'll know we spent quite a bit of time with our hardware partners making sure we that this works the way it should. Damn that was a long post! Sorry this subject has just irrititated me lately seeing all these devices and knowing that they would not work making me feel as if these companies are knowingly taking money from people selling something that doesn't work. Darrius Thompson Director R&D DivX
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Darrius DivX Co-Founder Last edited by Darrius "Junto" Thompson; 13th June 2003 at 01:07. |
16th June 2003, 17:30 | #4 | Link |
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Junto: is there a list of officially certifed players somewhere on your site? I'm sure that would help people make the right choice.
Also, can you tell us a little bit more about what is required to get the certification. For instance, I was told be an elta employee, that a DivX3 capable firmware would be released as soon as DivX Network certification would be complete. This got me wondering, after all, I don't see DXN having a particular interest in playing anything but their own codecs. I also heard from mecotek that their DivX3 supporting firmware would be out pending a DXN certification. Also, about your profiles. It looks like the home theater profile only allows for bitrates up to 4mbit. What's the reason behind this? In certain scenes, codecs take 6mbit or more if they can, certainly not a bad thing when the VBR algorithm has been properly implemented. And, the elta appears to play Quantizer2 DivX5 clips with GMC just fine (I obviously had to deactivate any profile to encode using those settings). Unfortunately it appears that if XviD testing were even less important for manufacturers, and since XviD offers a more complete implementation of the advanced simple profile (multiple b-frames for instance), the full use of those features hardly works. I hope that one day there'll be an industry standard for MP4 standalones because the way it looks now, months after the first device has come out, neither codec is fully supported and there's no date for a firmware that can handle all the advanced simple profile features.
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16th June 2003, 22:58 | #6 | Link | |||||
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Great questions. Hopefully I can answer them all adequately.
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There are 2 levels of requirements for manufacturers working with us. 1. DivX Compatibility and 2. DivX Certification. We plan on requiring everyone to be DivX Certified soon but one of the problems has been the DivX3 compatiblity issue. The 2 Requirements are identical however "Compatiblity" does NOT require the ability to decode DivX3 but DivX Certification does. We created DivX Compatiblity so that we could get devices available to users as soon as possible. DivX3 required quite a bit more work since it is not MP4 so it is technically very challenging and it pushed the timeline substantially for getting DivX\MP4 devices into the hands of DivX users. We decided to create a DivX Compatiblity Requirement so we could certify products that meet a mininum set of requirements minus DivX3 for at least the very near future so there are at least products that can decode DivX4,5 well and at the same time we will move toward ONLY having a "DivX Certfication" of which DivX3 decoding is a requirement. Quote:
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One good example of some of this oversite is the MP4 file format. It sounds great and could be great. Try implementing it in hardware So as many of you know it is based off of QT. The MP4 file format keeps all of it's important timing data in one location\chunk, etc.. at the beginning of a file and must be indexed to achieve proper audio\video\data synch. A movie a few megs could have a couple hundered kbytes of index date. AVI although old, has simple interleaving which does not require this. So imagine having a 2 hour movie in the MP4 file format and trying to support it in a DVD\DivX type of player. What happens is for proper synch you have to keep all this index data stored in memory during playback PLUS have enough memory to handle playback (video data). The index data alone can be > 8MB and then you add in what is needed for video playback, menus, etc.. and you have a device that is going to be expensive to build because of a large memory requirement. So for the near future there is a cost problem of even building consumer devices at reasonable costs that support everything that is required for the mp4 standard. Many seem to be moving very slow and not necessarrilly thinking of the big picture which includes cost of implementation not including licensing cost and not also thinking about what users need\want at a minimum. Sorry such a long description I just wanted to list *one* example of how complex this has been and how it is not just a basic technology issue we have to try and overcome. This is just ONE example. Damn this has been tiring.... yet fun. We've tried our best to push things foward more rapidly so that good products are available soon which are *useable* rather than wait for what could be forever before we see good technology put to use. So as you can see we could only wish there was a standard that everyone could agree upon and that not only seems to work well but can actually be implemented in software and devices at acceptable price points with latest technologies. Anyways we're at least doing one thing.... we're helping to push technology foward given all the roadblocks we've had to work with our partners and the DivX community to help overcome There are some great people out there trying to make good things happen. When I say "we" I also mean the hardocore video enthusiast out there also pushing us and others to make things happen. Hope this helps. Darrius Thompson Director R&D DivX
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Darrius DivX Co-Founder Last edited by Darrius "Junto" Thompson; 17th June 2003 at 01:07. |
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17th June 2003, 07:52 | #7 | Link |
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about QPel and GMC: some would argue that first offering those features, then making them optional in the profiles introduced with 5.04 is a step backward and does not take care of the existing userbase of those features. While theoretically I'm inclined to agree that those features don't do much good, at least in the GMC case, QPel in XviD isn't so bad anymore - it's more a matter of getting used to a different look.
Also, what about XviD? Theoretically a decoder should be able to handle both, but since XviD's implementation is more complete (multiple b frames for instance - I've just verified yesterday that using 2-3 b-frames can lead to slight jerkyness in some cases whereas 1 b-frame, as in divx5, works just fine in my standalone). What does your certification require towards that end? How many consecutive b-frames have to be supported? And while we're at the subject, do you do any testing for GMC and QPel support? And if you're in the market for a player that does it all (full MPEG-4 advanced simple profiles support, full DivX3 support), what kind of logo does he have to look for? I suppose DivX home theatre profile isn't enough since that only covers DivX5 with 1 b-frame. Last but not least, the KISS player seems to be having problems with DivX3 clips in some instances.. is it DivX certified?
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17th June 2003, 17:23 | #9 | Link | ||||
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Certification does require support for B-frames. However support more than 1 B-frame has not been explicity stated and so then is not a minimum requirement. We were just recently looking at support for multiple b frames and what we have found is a very similar issue.... more complexity when in hardware. There may have to be substantial optimization for some hardware along with different memory requirements for referencing additional b-frames. It's interesting since I would have expected that when vendors built their generic MP4 decoders this would have been taken into consideration. Anyways, support for multiple b-frames is currently not required but we are investigating support. Did you try multiple b-frames on the Kiss Player? Or has anyone else? I would expect it to almost always work but depending on hardware exhibit the "jerkiness" you mentioned due to memory and indexing of frames in hardware. So *currently* 1-Bframe must be supported however that doesn't mean a manufacturer might not explicity support more than 1 properly. Quote:
When we certify hardware we have a set of test cases and test clips that we push through the hardware for hardware verification\testing. And so yes there is testing for GMC and Qpel especially if these features are implemented. If they are not this becomes a test for how the prdouct will handle these features (error conditions). We currently do not have a logo or program that designates full MP4ASP+DivX3 because of the reasons described above. It may not technically be feasible for a considerable time on a non-pc device within a price range most of us could afford within the consumer price range that can support these features. Yes this sucks but right now it's a limitation of not having hardware that can handle the power needed for all these features. Quote:
As soon as devices are certified you can be sure we will be making announcements since it will really be milestone for us after all this time and work. We acually have a meeting today to discuss getting this information on DivX.com as soon as possible along with a section that list products that are certfied. The logo looks very similar to the badges seen on divxnetworks.com. http://www.divxnetworks.com/certified/about.php One question I have for everyone. Of course we (DivX) will certfify the product to ensure that DivX certfication is met, however there are other features that are also important in a DivX\DVD\XviD player such as Menu's\GUI, Navigation, Audio Support, Network Connectivity, Qpel, GMC and multiple B-frame support. It could be a conflict of interest if we were to do a review that also gives everyone feedback on all these features. It would be best if this feedback came back from a neutral and reliable third party. This type of review may happen on its own or we could help find the right people, site, or company to start doing 3rd party reviews. This is alread somewhat happening via the forums here and at divx.com but not in a manner that makes it easy for eveyrone to quickly see. Thoughts on how this might be approached? Darrius Thompson Director R&D DivX
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17th June 2003, 18:32 | #10 | Link | |
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as for the rest, this is indeed something that should be handled by a 3rd party, though how exactly I do not know. I have found myself critisizing major websites for their hardware testing because they didn't use the right divx encoding tool, or didn't publish all their parameters (and sometimes their results simply didn't make sense). The community was once working on common speed test sets but that never got anywhere either so I'm not sure if a common test case can be established at all. It takes a strong entity to pull this off and I don't see any that has enough respect where it matters (community and the industry).
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17th June 2003, 18:59 | #11 | Link | |
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Thanks for the feedback on the review issue. So we will only be able to state if the product is certfied and hopefully there will be a reliable source for a true product review. What if we setup a system\site or payed for someone else to do this that allowed for user feedback\ratings similar to how cnet works? Darrius
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Darrius DivX Co-Founder Last edited by Darrius "Junto" Thompson; 17th June 2003 at 19:01. |
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17th June 2003, 19:40 | #12 | Link | |
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And a standard for both software and hardware developers already exists: either the standard mpeg-4 advanced simple profile is supported by both software and hardware developers or not! I think it would be better to push open standards like mpeg-4 to enable competition and support for all standard compliant codecs, which would be the best for most of us ! sorry, but i am sceptical about things like inventing new standards like a "divx certification". what about insuring support for xvid or other mpeg-4 standard compliant codecs, which can be better than divx5?
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17th June 2003, 20:20 | #13 | Link | ||
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Would you rather have NO ONE creating any sort of certification so that you might go to the store and buy one device that only support MP4 SP and then another that supports MP4 SP but only at 800kbps, and then another that supports MP4 + Only GMC, and etc...? Look at some devices being sold today.. you'll see in small print that it says DivX\MP4 ASP\Xvid and so you think it's great. You then spend $500 and notice that the small print says MP4 ASP (does not include GMC, Qpel, DivX3, MP4 File Format). This really bothers me that this is happening where consumers are in a way tricked into buying something that might not be what they expected. With certfication you will at least know what to expect. The hardware is the limitation and so we have to decide what are the best features to squeeze into that hardware. Someone has to try and get everyone on the same page so we can understand what to expect out of these products and what the best features are for the product given the hardware limitations otherwise it will get quite confusing. This is the problem today. Instead of continuing to go into any more detail here I'm going to spend my time creating an FAQ and Page on DivX.com that should contain all this information and more. This thread has been very useful. Thanks everyone. If there are other open questions please send them to me or post them here and I'll get them added to the site. We will detail exactly what our certification process is on the described page along with many of the questions that have been asked here and of course list the compatible and certified products. Darrius
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17th June 2003, 23:48 | #14 | Link | |
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18th June 2003, 01:53 | #15 | Link | |
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-- bobololo. ps: btw do you plan to fix the qpel chroma rounding in DivX 5.x and comply with N5546 ? Last edited by bobololo; 18th June 2003 at 02:01. |
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18th June 2003, 08:08 | #16 | Link |
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What about Matroska support as well as MP4ff ? You were talking about menus system, matroska will support all of this and even more, is patent free and a system like control track would be very interesting on a set top box player.
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18th June 2003, 10:26 | #17 | Link | |
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I guess some of the cost of the MPEG 4 hardware codecs has to be down to the quantities they must be selling. It costs a heck of a lot to develop a chip. I am sure as time goes on and the market grows that the price will fall. Very interesting thread. Thanks to Doom9 and Darrius. |
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18th June 2003, 12:10 | #18 | Link | |
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The firmware is still at a very early stage and kiss seem to be spending more time creating new models rather than getting the firmware sorted out. 3.11 support is nice but I would like to see a specific set of encoding tests for divx5 (maybe you could release these so we can test them on our own players). Ie proven encoding methods that will have no problems with playback. |
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18th June 2003, 12:18 | #19 | Link |
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Some problems that I can see with the kiss players and Divx certification:
1) VBR audio is still not at a stage where you can say it will stay in sync every time. Something to do the number of key frames i think. 2) The search functions still dont work too a high enough standard for every day use. (only timesearch and very unreliable) 3) Divx Aspect ratio's are all over the place. Three very important features of a playback machine I would think. |
19th June 2003, 00:32 | #20 | Link | ||
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As mentioned already it currently does NOT meet certification requirements *yet*. You mentioned some of the hiccups in your other message and Quote:
Darrius
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