[Matroska-devel] mkvalidator cluster/cues validation

michael.steen.jensen at tdcadsl.dk michael.steen.jensen at tdcadsl.dk
Tue Aug 16 18:22:19 CEST 2011


Hi Steve

Thanks for the reply.

Just to explain:

Could easily change my MKV muxer so the warnings disappears - aligning the 
clusters on video key-frame boundaries. However for highdef video files this 
is likely to cause an even more serious problem than
say slow seeking - namely that playing the file does not work properly. If 
the cluster size gets too big, players like VLC most likely ends up flushing 
its buffers periodically and playback suffers.

So the recommended way must be to keep the clusters at a reasonable size say 
512kb .. 1.5Mb and not necessarily align the clusters on video 
key-boundaries.

The matroska format seems to be prepared for this approach via the 
CueBlockNumber so the mkvalidator warning,  still makes little sense to 
me...

Using the CueBlockNumber a player could easily skip the specified number of 
blocks in order to find the "keyframe block" - and yes, its probably just as 
easy without the CueBlockNumber information :-)

/MSJ



----- Original Message ----- 
From: "Steve Lhomme" <slhomme at matroska.org>
Newsgroups: gmane.comp.multimedia.matroska.devel
To: "Discussion about the current and future development of Matroska" 
<matroska-devel at lists.matroska.org>
Sent: Sunday, August 14, 2011 4:13 PM
Subject: Re: mkvalidator cluster/cues validation


> It is a warning because it's not optimal for seeking. A lot of data
> will be read for nothing in this case, unless the Cluster is not
> referenced in the Cues and if the Cues are not damaged.
>
> I don't think there are much players that make use of the
> CueBlockNumber element at all.
>
> Steve
>
> On Wed, Aug 3, 2011 at 9:20 AM,  <therealmsj at gmail.com> wrote:
>>
>> mkvalidator complains about "first block for video track # not being a
>> key-frame". Its only a warning but why complain about
>> something thats totally valid - in this case the CueBlockNumber points at
>> the key-frame block. I could understand the warning if the
>> CueBlockNumber element had not been present or was pointing at the wrong
>> block.
>>
>> what seems to be missing from mkvalidator is a "cues key-validation" - if
>> the first block is not a video key-frame and CueBlockNumber is not
>> present it should generate a warning. A warning because there does not 
>> seem
>> to be any requirement that cues should only contain references
>> to key-frames. Also, mkvalidator seems to ignore the CueBlockNumber -
>> writing a wrong block number does not generate any error.
>>
>> please comment.
>>
>> Thanks in advance
>>
>> /MSJ
>>
>>
>>
>>
>>
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>>
>
>
>
> -- 
> Steve Lhomme
> Matroska association Chairman
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