[MPlayer-users] Size of MP4 video not correctly recognized.

[Richard S.]

Hernan Badino schrieb:
> Richard S. wrote:
>> Hernan Badino schrieb:
>>  
>>>> The metadata(moov box/atom) of your mp4 file is wrong. The width and
>>>> height is set to 320x240.
>>>> http://img218.imageshack.us/my.php?image=wrongwidthandheight1xb2.png
>>>> http://img151.imageshack.us/my.php?image=wrongwidthandheight2xx1.png
>>>> Remux your file with MP4Box( http://gpac.sf.net )
>>>> MP4Box -add oldfile.mp4 newfile.mp4
>>>> Richard
>>>>       
>>> Hallo Richard,
>>>
>>> Thanks for the help.
>>>
>>> Yes, it seems that width and height are wrong. What I don't understand
>>> is way could I play the file correctly with some previous version of
>>> mplayer. Currently I can also play the file correctly with mediaplayer
>>> in windows and the 3ivx codec. And even quicktime can play the file.
>>> So, how do they do it? They just "guess" the right size?
>>>
>>> Hernan
>>>     
>> This player(Quicktime)/dshow filter(3ivX) seems to ignore the wrong
>> information from the container and use the information from the video
>> elementary stream.
>> This way they can handle files with wrong information in moov ... .
>>
>> In ISO/IEC 14496-12(ISO Base Media Format) you will find this for:
>>
>> http://img218.imageshack.us/my.php?image=wrongwidthandheight1xb2.png
>>
>> width and height specify the track's visual presentation size as
>> fixed-point 16.16 values. These
>> need not be the same as the pixel dimensions of the images, which is
>> documented in the sample
>> description(s); all images in the sequence are scaled to this size,
>> before any overall transformation of
>> the track represented by the matrix. The pixel dimensions of the images
>> are the default values.
>>
>>
>> http://img151.imageshack.us/my.php?image=wrongwidthandheight2xx1.png
>>
>> width and height are the maximum visual width and height of the stream
>> described by this sample
>> description, in pixels.
>>
>> In ISO/IEC 14496-14( MP4 File Format)you will find this:
>> In MPEG-4 both visual and aural composition are done using the BIFS
>> system. Therefore structures marked as “template” in the ISO Base Media
>> Format which pertain to composition, including fields such as matrices,
>> layers, graphics modes (and their opcolors), volumes, and balance
>> values, from the MovieHeaderBox and TrackHeaderBox, are all set to their
>> default values in the file format. These fields do not define visual or
>> audio composition in MPEG-4; in MPEG-4, the BIFS system defines the
>> composition.
>> The fields width and height in the VisualSampleEntry and in the Track
>> Header Box shall be set to the pixel dimensions of the visual stream.
>>
>> Richard
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>> MPlayer-users at mplayerhq.hu
>> http://lists.mplayerhq.hu/mailman/listinfo/mplayer-users
>>
>>   
> Hello Richard,
>
> thanks again for your detailed answer. You are the expert and you are
> right that the file is corrupt. Nevertheless, what I find terribly
> good in mplayer is its robustness. It can play almost everything. I
> agree that one has to follow ISO specifications, but, wouldn't be nice
> to dote mplayer with such a "wrong header parameter detection"? I
> mean: 3/4 of the information is ignored (or at least not displayed)!
>
> Hernan
I am not a MPlayer developer, it's up to one of the developers, how to
handle this.
I would correct this file with MP4Box. You can never know, how other
players will handle  such a file  in the future.

Richard