[Spice-devel] Streaming video command line

[Alon Levy]

On Thu, Apr 21, 2011 at 10:22:15AM +0200, Andrea Celestino wrote:
> Thanks.
> Now I am trying to study the code I am interested in.
> Unfortunately, the file red_worker.c is very huge and there are not any
> comments that can help me.
> 
> I would like to know:
> 1- which parts/functions of red_worker.c are video related stuff?
A lot. Seriously - this requires a little more checking then I can give you off
the top of my head. Questions 2 and 3 are more specific, so easier to answer.
I would seriously suggest trying systemtap or just adding some prints to see
what is going on. Start from red_process_drawable.

> 2- You said:
>  "determine if a given draw operation (has to be an opaque copy iirc) is
>  repeated to the same area."
> What do you mean with "opaque copy iirc"?

iirc - if I recall correctly, meaning I'm not sure.
opaque copy - an operation that copies a bitmap to a surface. The video streaming
is done based on seeing repeated operations that copy a bitmap to the same
surface, always surface 0 (that is the primary surface, we ignore repeated copies
to non primary surfaces).
opaque - meaning the destination bits are overwritten by the source bits, no binary
operation is done (xor/and/or).

> 
> 3- There are a red worker thread for each QXL device instance. How many QXL
> device instance are there?

One per device. But you can ignore the support for multiple devices for this,
so just one if you run a single device ("-vga qxl").

> 4- Which function does red_worker.c use to detect video streaming?
> 
interesting functions are:
__red_is_next_stream_frame
anything with ->stream
red_attach_stream
anything with mjpeg
red_current_add, the bottom part (that checks for OPAQUE and calls red_use_stream_trace)

> Thanks for any helps you can give me
Sure, please take a look at the above points and try what I suggested.

Alon

> 
> 2011/4/15 Alon Levy <alevy at redhat.com>
> 
> > On Thu, Apr 14, 2011 at 03:20:40PM +0200, Andrea Celestino wrote:
> > > I would like to improve the streaming video performance in Spice, do you
> > > think that is possible to improve it? In what way?
> > > Are there documents that describes in detail how spice works with video?
> >
> > The best I can offer in terms of documentation is the pdfs in the documents
> > section of spice-space.org, I imagine you are looking for something more,
> > sorry to disappoint.
> >
> > The code you are interested in is server/red_worker.c, but that's not very
> > helpful since that file is huge. Would be nice to split the video related
> > stuff to a separate file.
> >
> > worker->streaming_video - determines how we handle streaming video
> >
> > git grep stream -- server/red_worker.c
> >
> > I can give you better pointers if you ask more specific questions, but
> > doing
> > the documentation myself right now.. too much work.
> >
> > overview of what spice does:
> >  * determine if a given draw operation (has to be an opaque copy iirc) is
> >  repeated to the same area.
> >  * if so, starts a mjpeg encoder and sends the stream to the client
> >
> > how to improve this (some is on the Features page in spice-space):
> >  * learn to do various video acceleration apis (windows has it, linux has
> > it)
> >  * this is by far the best way to go regarding performance, unless you are
> >  willing to sacrifice cpu for bandwidth in which case I guess you would
> > reencode.
> >  * otoh this is a pretty large change to multiple parts of spice:
> >   * you need to update the driver for each platform you choose to support,
> > update the protocol, teach server and client
> >  * it's definitely on the todo list, but no date set.
> >  * replace mjpeg with a different encoder
> >  * if it's just a better performing encoder, clear win.
> >  * otherwise you get the usual cpu/bw tradeoff.
> >  * or you could try to learn which encoder fits which stream (based on some
> >  metric, could be the performance of the encoders themselves)
> >   * just throwing an idea.
> >
> > Alon
> >
> > >
> > > 2011/4/11 Alon Levy <alevy at redhat.com>
> > >
> > > > On Mon, Apr 11, 2011 at 03:48:08PM +0200, Andrea Celestino wrote:
> > > > > Hi,
> > > > > I have installed Spice and now I'm trying to use it. I'm interested
> > in
> > > > how
> > > > > spice manage streaming video. I read that there is the option
> > > > >
> > > > > -streaming-video=[all|off|filter]
> > > > >
> > > > > Can you explain me the difference between these three option?
> > > > > Which source file read the command line?
> > > > > Why I have tried to play a video in a player but i have not notice
> > any
> > > > > difference between the two options 'off' and 'filter'?
> > > > >
> > > >
> > > > Look at
> > http://cgit.freedesktop.org/spice/spice/tree/server/red_worker.c
> > > >
> > > > search for STREAM_VIDEO_FILTER
> > > >
> > > > The switch toggles modes for creating streams:
> > > >  off - never create
> > > >  all/filter - create either based on smallest size, or just based on
> > > >  number of consecutive opaque copies to same area.
> > > >
> > > > > Thanks very much for the help.
> > > >
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> > > >
> > > >
> >
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> >