[Mp4-tech] MPEG4 Systems.. VisualSampleEntry

[Dave Singer]

At 10:52 AM +0530 10/8/04, veni soc-soft.com wrote:
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>Folks,
>
>Can someone tell me about the mystery of VisualSampleEntry. In the 
>specs all fields are reserved with some values(useful one like 
>height width etc like quick time file format). Can anyone give me 
>the exact defination of VisualSampleEntry for mpeg4 video.
>
>veni
>enJOY life

class VisualSampleEntry(codingname) extends SampleEntry (codingname){
	unsigned int(16) pre_defined = 0;
	const unsigned int(16) reserved = 0;
	unsigned int(32)[3]	pre_defined = 0;
	unsigned int(16)	width;
	unsigned int(16)	height;
	template unsigned int(32)	horizresolution = 0x00480000; 
	// 72 dpi
	template unsigned int(32)	vertresolution  = 0x00480000; 
	// 72 dpi
	const unsigned int(32)	reserved = 0;
	template unsigned int(16)	frame_count = 1;
	string[32]	compressorname;
	template unsigned int(16)	depth = 0x0018;
	int(16)	pre_defined = -1;
}
class MP4VisualSampleEntry() extends VisualSampleEntry ('mp4v'){
	ESDBox	ES;
}
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.
The esds box contains an ES Descriptor and so on;  the decoder config 
descriptor is the VOL header etc. for the stream, without any 
trailing end code sequence.
Hope this helps.
-- 
David Singer
Apple Computer/QuickTime
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