What is Restricted system 4CC `ress`?

[podborski]

https://github.com/MPEGGroup/FileFormatConformance/blob/2aefa1e1a865bea24c235c7a265da61db68a5c00/data/standard_features/14496-12/boxes.json#L1134C24-L1134C24

@cconcolato do you know what this is? @DenizUgur not so sure where it came from, do you remember?

[DenizUgur]

That was something we left for future Dimitri and Deniz to handle. AFAIK, specification was either not correct or had missing information

[DenizUgur]

ress , encs, rest, and resu were the problematic ones

[podborski]

Found this table in the 8th edition draft of ISOBMFF:

Stream (Track) Type	Sample-Entry Code	SampleEntry Class
Video	resv	VisualSampleEntry
Audio	resa	AudioSampleEntry or AudioSampleEntryV1
Metadata	resm	MetaDataSampleEntry
Text	rest	SimpleTextSampleEntry
Subtitle	resu	XMLSubtitleSampleEntry
Systema	ress
Font	resf	FontSampleEntry
Haptics	resp	HapticSampleEntry
Volumetric visual	res3	VolumetricVisualSampleEntry

The sample entry type for ress is not provided and I have no idea what it should be. Perhaps just a simple SampleEntry?

[DenizUgur]

Let me also transfer our findings from that time here:

rest: Syntax from ISOBMFF Table 8 seems to refer to wrong SampleEntry class. It should be PlainTextSampleEntry
resu: Probably it should be SubtitleSampleEntry
ress: Not clear
encs: See rest

[podborski]

Ah, it points to Part 14

aligned(8) class ESDBox 
	extends FullBox('esds', version = 0, 0) {
	ES_Descriptor	ES;
}
	// Visual Streams

class MP4VisualSampleEntry() extends VisualSampleEntry ('mp4v'){
	ESDBox	ES;
}
	// Audio Streams

class MP4AudioSampleEntry() extends AudioSampleEntry ('mp4a'){
	ESDBox ES;
}
	// all other Mpeg stream types
class MpegSampleEntry() extends SampleEntry ('mp4s'){
  ESDBox ES;
}

So I guess we can define ress having 3 types as shown above.

[DenizUgur]

That's fine, we just need to create new entries then

[podborski]

rest: Syntax from ISOBMFF Table 8 seems to refer to wrong SampleEntry class. It should be PlainTextSampleEntry
resu: Probably it should be SubtitleSampleEntry

I believe the question here is if it should be more generic. I'm not sure. I kind of suspect it should.

For example, There are 2 classes that derive from SubtitleSampleEntry

• XMLSubtitleSampleEntry
• TextSubtitleSampleEntry

but only XMLSubtitleSampleEntry is allowed to be encrypted / restricted? This was the reason why I thought it should be the base class.

encs: See rest

It is similar to ress