[Matroska-devel] multiple video streams stereo 3D mode broken

Dorian Muthig contact at dorianmuthig.com
Sat Feb 5 14:23:34 CET 2011


Hello,

Well, the thing is side-by-side formats are growing popular now since that's how the revised VC-1 and AVC specs are doing it to achieve better compression. This means there needs to be new playback software that supports those formats and I don't see how to do this according to the specifications, since enabling the proper support with Matroska would break the old formats. It would be much better if it were possible to implement a worry free solution. There are a few people who are unwilling to upgrade for reasons unknown, along the lines of "Why fix it, if it isn't broken?".

Best regards,

Dorian Muthig
IT & Intelligence Services
Phone: +49 1522 9290158 (callerID required)
Twitter: @dorianmuthig
contact at dorianmuthig.com
 Please consider the environment before printing this document!


-----Original Message-----
From: Steve Lhomme [mailto:slhomme at matroska.org] 
Sent: Saturday, February 05, 2011 1:50 PM
To: Dorian Muthig
Cc: Matroska Devel
Subject: Re: multiple video streams stereo 3D mode broken

Mm, this is embarrassing. I wish we had the info that people were actually using the StereoMode feature already. Especially now that we have release libmatroska and mkvtoolnix.

Still, is there a single custom player that handles these files or many ? Can you point me to the people who are doing it ? There might be ways to work things out on the technical side. If they only support separate tracks and not side by side, then all the files they would encounter with the newer values would contain the TrackOperation element. And for old files/muxers it would be StereoMode 1 and 2. So that could be the "easy" detection. Of course this breaks if they support side by side as defined in values 1 and 2.

Steve

On Sat, Feb 5, 2011 at 12:33 PM, Dorian Muthig <contact at dorianmuthig.com> wrote:
> Hello,
>
> A few production solutions use a custom muxer for video stream to MKV recording with the indexes added after recording completion, but the application of choice was mostly Haali's DS Mux due to mkvmerge's problems with the VC-1 codec bitstream, some types of AVC and all types of AVS (popular in China and only used in entirely custom solutions), the unsupported tags have in that case been added later via a header and tag editor. The Matroska headers are very minimalistic in some cases and do not include the parameter for the writing application.
> As for the viewing angles, those are usually referenced in the track title or chapters, since there's no property in the specifications for that. More common are different aspect ratios, resolutions and video languages, which can be easily detected via the appropriate meta data and simple logic. In order to fool the detection for the old format you would have to intentionally make a file with incorrect parameters for language and aspect ratio or image size. Whilst this can occur, it is more likely that those parameters are missing and only the needed streams (left and right video plus audio) are included in one file due to laziness of the file author.
>
> Best regards,
>
> Dorian Muthig
> IT & Intelligence Services
> Phone: +49 1522 9290158 (callerID required)
> Twitter: @dorianmuthig
> contact at dorianmuthig.com
> P Please consider the environment before printing this document!
>
> -----Original Message-----
> From: Steve Lhomme [mailto:slhomme at matroska.org]
> Sent: Saturday, February 05, 2011 10:58 AM
> To: Dorian Muthig
> Cc: Matroska Devel
> Subject: Re: multiple video streams stereo 3D mode broken
>
> Moving the discussion to the list at some other people may be interrested.
>
> On Fri, Feb 4, 2011 at 6:49 PM, Dorian Muthig <contact at dorianmuthig.com> wrote:
>> Hello,
>>
>> Whilst converting a local library to the new format wouldn't be much of a problem, for files from a remote source I still can be sure about the format used, especially since people don't usually update their muxing software regularly and stick to what they know and rely on.
>> The old format made sense very well. If the first or default video is a stream with stereo mode set to 1 or 2, I need to look for the second complementary stream that uses the stereo mode for the other eye. The playback software then combines the picture from both streams into a display or projector output for stereoscopic viewing.
>> There may not have been a large consumer space for 3D viewing at home at the time, but small production environments and 3D movie theaters have used the format due to its codec versatility.
>
> I understand. But it should not be left to guessing which track should be combined with what other. Imagine you have 2 right eye and 2 left eye tracks (for example a multi angle video). There was nothing to know which should be used.
>
> I think it's too late now to change the values again (and leave empty the fields that were used). So since such systems use a custom player, I guess they can be updated to check which mkvmerge value was used (unless they also used custom muxers). It's not much more complex than checking for a new field. Such players should also be updated to handle the new TrackOperation system too.
>
> I'll add in my TODO a tack to make the mkvmerge check and StereoMode fix.
>
> Steve
>
>> Best regards,
>>
>> Dorian Muthig
>> IT & Intelligence Services
>> Phone: +49 1522 9290158 (callerID required)
>> Twitter: @dorianmuthig
>> contact at dorianmuthig.com
>> P Please consider the environment before printing this document!
>>
>>
>> -----Original Message-----
>> From: Steve Lhomme [mailto:slhomme at matroska.org]
>> Sent: Friday, February 04, 2011 1:55 PM
>> To: Dorian Muthig
>> Subject: Re: multiple video streams stereo 3D mode broken
>>
>> If necessary If can add a feature to mkclean to turn old files into new ones, assuming they are made with older mkvmerge versions.
>>
>> The old system with one side of the stereo per track without anything to tell how they are combined is just not good. It was there as a placeholder a long time ago before we had any idea how 3D would be used. It's sad that mkvmerge presented the feature when it was really not considered stable.
>>
>> On Fri, Feb 4, 2011 at 12:37 PM, Dorian Muthig <contact at dorianmuthig.com> wrote:
>>> Hello,
>>>
>>> I was planning on updating a system to the new specifications and this caused a conflict with existing use that would render the system effectively useless upon change.
>>>
>>> Best regards,
>>>
>>> Dorian Muthig
>>> IT & Intelligence Services
>>> Phone: +49 1522 9290158 (callerID required)
>>> Twitter: @dorianmuthig
>>> contact at dorianmuthig.com
>>> P Please consider the environment before printing this document!
>>>
>>>
>>> -----Original Message-----
>>> From: Steve Lhomme [mailto:slhomme at matroska.org]
>>> Sent: Friday, February 04, 2011 12:18 PM
>>> To: Dorian Muthig
>>> Subject: Re: multiple video streams stereo 3D mode broken
>>>
>>> I know changing something that was potentially used is bad. But do you actually know a system that was using the old specs ? You seem to be talking about a system, but not that it is actually using 3D inside Matroska.
>>>
>>> According to this http://www.matroska.org/node/1/revisions the StereoMode values were changed in September 2010.
>>>
>>> On Fri, Feb 4, 2011 at 12:12 PM, Dorian Muthig <contact at dorianmuthig.com> wrote:
>>>> Hello,
>>>>
>>>> Thank you for your quick reply.
>>>>
>>>> I do not know of any consumer software, but I am aware of a few custom solutions utilizing polarized projection systems that feed separate video streams to two projectors. The problem is, files created according to the old specifications played back with software of the new specification, would discard the second video stream and display garbage on the first display. It further renders the parameters 1 through 3 for video streams of the new kind useless and requires a computationally expensive or at least inefficient way to detect the stereoscopy format. This means if I want to support both formats, I need to find additional metadata or analyze the picture before deciding to split the picture or loading the second video stream, which according to the new specifications is more likely to contain a different and optionally alternate choice of content.
>>>> Adding new functionality is good. Removing and replacing functionality under the assumption nobody used it, is always a bad idea.
>>>>
>>>> Best regards,
>>>>
>>>> Dorian Muthig
>>>> IT & Intelligence Services
>>>> Phone: +49 1522 9290158 (callerID required)
>>>> Twitter: @dorianmuthig
>>>> contact at dorianmuthig.com
>>>> P Please consider the environment before printing this document!
>>>>
>>>> -----Original Message-----
>>>> From: Steve Lhomme [mailto:slhomme at matroska.org]
>>>> Sent: Friday, February 04, 2011 11:23 AM
>>>> To: Dorian Muthig
>>>> Subject: Re: multiple video streams stereo 3D mode broken
>>>>
>>>> Are you aware of any software that could play files the old values ?
>>>>
>>>> On Fri, Feb 4, 2011 at 8:53 AM, Dorian Muthig <contact at dorianmuthig.com> wrote:
>>>>> Hello,
>>>>>
>>>>>
>>>>>
>>>>> In the new revision of the specifications in regard to the 
>>>>> StereoMode field there is an issue with backward compatibility. 
>>>>> The earlier spec defined 0 (no stereo/mono), 1 (left), 2 (right), 
>>>>> 3 (both). While there is no change for non-stereo content, it is 
>>>>> no longer possible to use two separate video streams and content 
>>>>> creating the format would no longer play correctly on playback 
>>>>> software written according to the new specifications. You should 
>>>>> keep the old modes and only have added the new ones for the 
>>>>> consumer playback formats. In production environments it is common 
>>>>> to keep the video streams separately (modes
>>>>> 1 and 2) or to define the type of stereo mode used in the video 
>>>>> stream headers (mode 3). For backward compatibility those settings 
>>>>> should have remained as is and the new settings be amended 
>>>>> starting with mode 4, resulting in 14 total modes. While 
>>>>> TrackCombinePlanes are a solution for new content with separate video streams, they do not solve the playback problem with files muxed according to the old specification.
>>>>>
>>>>>
>>>>>
>>>>> Best regards,
>>>>>
>>>>>
>>>>>
>>>>> Dorian Muthig
>>>>>
>>>>> IT & Intelligence Services
>>>>>
>>>>> Phone: +49 1522 9290158 (callerID required)
>>>>>
>>>>> Twitter: @dorianmuthig
>>>>>
>>>>> contact at dorianmuthig.com
>>>>>
>>>>> P Please consider the environment before printing this document!
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Steve Lhomme
>>>> Matroska association Chairman
>>>>
>>>
>>>
>>>
>>> --
>>> Steve Lhomme
>>> Matroska association Chairman
>>>
>>
>>
>>
>> --
>> Steve Lhomme
>> Matroska association Chairman
>>
>
>
>
> --
> Steve Lhomme
> Matroska association Chairman
>



--
Steve Lhomme
Matroska association Chairman
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