Re: [libmicrohttpd] JPEG Streaming with libmicrohttpd

[Christian Grothoff]

On Thursday, November 11, 2010 06:41:47 pm David J Myers wrote:
> So you don't need to call MHD_queue_response for each frame? Just copying
> the data into the buffer in the callback is enough to send the data to the
> client? What about the inter-frame headers,
> --myboundary
> Content-Type: image/jpeg
> Do I just put these manually in the callback buffer at the start of the
> JPEG data? ie. not using MHD_add_reponse_header?

Yep.  MHD_add_response_header is only for the 'global' headers, MHD has no 
idea about 'inter-frame' headers.

Christian

> Thanks again
> David
> 
> 
> -----Original Message-----
> From: Christian Grothoff [mailto:address@hidden
> Sent: 11 November 2010 17:30
> To: David J Myers
> Cc: 'libmicrohttpd development and user mailinglist'
> Subject: Re: [libmicrohttpd] JPEG Streaming with libmicrohttpd
> 
> You do NOT create another response object, you simply return the next
> frame(s)
> the next time you are called.  If the next frame is not (yet) ready, you
> return zero (if in 'external select' mode) or simply block (if in
> thread-per-
> connection mode).
> 
> Best,
> 
> Christian
> 
> On Thursday, November 11, 2010 05:50:48 pm David J Myers wrote:
> > Ok, thanks again, Christian.
> > Just to get this straight then. In the Access Handler Callback, I call
> > 'MHD_create_response_from_callback' with
> > MHD_SIZE_UNKNOWN. Then call MHD_add_response_header to add my headers.
> 
> Then
> 
> > in the Content Reader Callback, I can fill in the JPEG data, but what
> 
> about
> 
> > subsequent frames? Do I create another response_from_callback and repeat
> > for each frame, or do I return zero from the Content Reader Callback so
> > that it calls me again for the same response? Can you add headers within
> > the Content Reader Callback?
> > Best regards
> > David
> > 
> > 
> > -----Original Message-----
> > From: Christian Grothoff [mailto:address@hidden
> > Sent: 11 November 2010 16:12
> > To: David J Myers
> > Cc: 'libmicrohttpd development and user mailinglist'
> > Subject: Re: [libmicrohttpd] JPEG Streaming with libmicrohttpd
> > 
> > Dear David,
> > 
> > You must use 'MHD_create_response_from_callback', not 'from_data'; use
> > MHD_SIZE_UNKNOWN for the size argument and your data will be transmitted
> > while
> > you're still (incrementally) creating the response.
> > 
> > Happy hacking,
> > 
> > Christian
> > 
> > On Thursday, November 11, 2010 04:35:06 pm David J Myers wrote:
> > > Hi Christian,
> > > Thanks for the response. The infinite method is the one I need, but
> 
> could
> 
> > > you give me a bit more detail on the MHD calls I need to make.
> > > 
> > > I don't understand how to send each response part ie how to make an
> > > incremental response. In my callback, I can call
> > > MHD_Create_response_from_Data then MHD_queue_response, multiple times,
> > > but these responses won't be sent until the callback returns which
> > > won't work.
> > > 
> > > Thanks again,
> > > David
> > > 
> > > -----Original Message-----
> > > From: Christian Grothoff [mailto:address@hidden
> > > Sent: 11 November 2010 15:04
> > > To: libmicrohttpd development and user mailinglist
> > > Cc: David J Myers
> > > Subject: Re: [libmicrohttpd] JPEG Streaming with libmicrohttpd
> > > 
> > > Dear David,
> > > 
> > > MHD does very little for you here.  You'll need to set the content type
> > > header
> > > (MHD_add_response_header) and then somehow create the response with the
> > > 
> > > 
> > > boundaries yourself.  Depending on the requirements of your
> > > application, you
> > > 
> > > can either create it in-memory a-priori (if the stream is fixed size
> > > and small) or incrementally with the possibility of making the stream
> > > infinite in
> > > size (choose there respective MHD method to create the response
> > > object).
> > > 
> > > Either case will work, and in either case MHD will not help with the
> > > formatting of the response.
> > > 
> > > I hope this helps a bit.
> > > 
> > > Best,
> > > 
> > > Christian
> > > 
> > > On Thursday, November 11, 2010 01:30:52 pm David J Myers wrote:
> > > > Hi, I'm new to libmicrohttpd and I want to implement a motion JPEG
> > > > stream. Could someone please show me how to build the following
> > > > responses ie. A multipart response stream. This is what I want to
> > > > send back to the client when I receive the GET :-
> > > > 
> > > > 
> > > > 
> > > > HTTP Code: 200 OK
> > > > Content-Type: multipart/x-mixed-replace; boundary=myboundary
> > > > 
> > > > --myboundary
> > > > Content-Type: image/jpeg
> > > > 
> > > > <JPEG Image data>
> > > > --myboundary
> > > > Content-Type: image/jpeg
> > > > 
> > > > <JPEG Image data>
> > > > --myboundary
> > > > .
> > > > 
> > > > 
> > > > 
> > > > Thanks for your time
> > > > 
> > > > David
> > > 
> > > No virus found in this incoming message.
> > > Checked by AVG - www.avg.com
> > > Version: 9.0.869 / Virus Database: 271.1.1/3248 - Release Date:
> > > 11/10/10 19:34:00
> > 
> > No virus found in this incoming message.
> > Checked by AVG - www.avg.com
> > Version: 9.0.869 / Virus Database: 271.1.1/3248 - Release Date: 11/10/10
> > 19:34:00
> 
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.869 / Virus Database: 271.1.1/3248 - Release Date: 11/10/10
> 19:34:00