MMS format

[lieuwe]

All,

I am having trouble understanding the structure of an MMS message within Symbian.

I am using an attachment manager to iterate through all the CMsvAttachment's for a particular message. So far so good. What I don't quite understand is how the SMIL attachment links to the other parts. Some messages contain SMIL with references like

<img region="Image" src="04032009282.jpg"/>

and indeed one of the other attachments will be called "04032009282.jpg"

However, I sometimes get SMIL with a reference like

<img src="cid:3000000B8C.jpeg"/>

(is that MM7?)

Now none of the attachments will have a name like the above, in fact the relevant attachment is called "att2.jpg", it's TMsvAttachmentId is 2.

How does the phone (that displays the message correctly) link the cid to att2.jpg (or attachment with id 2)?

I did notice that one can set DesC8Attribute's for each of the attachment parts. Would one of those contain the cid reference? I have not managed to iterate through the attributes either, I can see from the API description that there are set and get methods, but how would you know what the attribute is called in order to get it in the first place? I.e. how does one iterate through them? The cmsvattachment.h header declares the following:

class CMsvAttributeManager;

but I cannot find any API (or other) references to this.


Cheers,

Lieuwe

[symbianyucca]

I would quess people here are not that much doing MMS messaging at the moment, so you could maybe try googling MMS definition decumentations, and get the answer that way.

[lieuwe]

I normally google before I post here. Anyway, I am still stuck.

The only idea I have is checking the attributes that are part of a CMsvAttachment. One of them could be the cid. I think cid points to the Obex "Content-Id" header, but I am not sure where in the data structures symbian keeps this. I found a class CObexHeaderList that can be initialised from an attachment (ImportFromAttachmentL()) - but all the other methods here are protected, so I am not sure on how to use this class either.

So what I am left with is running a loop 0 - max_int and calling GetDesC8Attribute on the attachment with each value to see if it's there (but this is clearly not the correct way of doing it), and if so, check what the attribute value is.

Any ideas you guys have are welcome

[lieuwe]

Finally nailed it.

In case anyone is doing something similar:

Use a CMsvMimeHeaders object and call RestoreL(attachment). One can then retrieve all the mimeheaders, one of them will be "Content-ID" which is the reference to the cid in the SMIL file.

Why is it that Symbian works like this? Instead of a

CMsvMimeHeaders* CMsvAttachment::getMimeHeaders() or something you have to create a CMsvMimeHeaders object first (and know it even exists as the documentation is a bit sparse) and the initialise it from an attachment?

One other question that I have not figured out yet. I noticed that the SMIL is not always the first attachment for an MMS message. How would the phone know that this is the master attachment that has links to the others? (I am sure it doesn't just cycle through the attachments to search for a SMIL). I did notice that the mime header Content-ID for a SMIL attachment is set to "0000", but this may be a coincidence.

Lieuwe