[Matroska-devel] mkvalidator cluster/cues validation

Steve Lhomme slhomme at matroska.org
Wed Aug 17 13:21:10 CEST 2011


Have you tried the large Cluster approach ? That's what mkclean does
with --remux regardless of the Cluster and it works fine. I don't
think there are any player that loads a whole Cluster in memory
(although that's one of the original goal).

Steve

On Tue, Aug 16, 2011 at 6:22 PM,  <michael.steen.jensen at tdcadsl.dk> wrote:
> 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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>>
>
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-- 
Steve Lhomme
Matroska association Chairman



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