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

[Hernan Badino]

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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>
>   
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