The 1.0 plan

[Sebastian Dröge-7]

On Fri, 2010-12-03 at 09:09 -0800, wally_bkg wrote:

> I also think the best documentation is a working sample code, with decent
> comments.  The only way I could figure out how to interpret video data
> pixels in a buffer (either as a plugin or appsink) was to stumble around the
> source code for gstgamma and gstvideoscale.  
>
> Of course the data you get in a buffer depends on the caps, but am I the
> only one who thinks there has to be a better way than:
>
> [...]

For this you should use the libgstvideo API to get the video format,
width, height, rowstride, component widths/heights, component offsets,
pixel strides, etc. from the caps:
http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-libs/html/gst-plugins-base-libs-gstvideo.html


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[wally_bkg]

Sebastian Dröge-7 wrote

On Fri, 2010-12-03 at 09:09 -0800, wally_bkg wrote:

> I also think the best documentation is a working sample code, with decent
> comments.  The only way I could figure out how to interpret video data
> pixels in a buffer (either as a plugin or appsink) was to stumble around the
> source code for gstgamma and gstvideoscale.  
>
> Of course the data you get in a buffer depends on the caps, but am I the
> only one who thinks there has to be a better way than:
>
> [...]

For this you should use the libgstvideo API to get the video format,
width, height, rowstride, component widths/heights, component offsets,
pixel strides, etc. from the caps:
http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-libs/html/gst-plugins-base-libs-gstvideo.html

Actually it was the nested function call to get the caps that seemed goofy to me.   I still need to do that on the buffer to use most of these API functions.

Unfortunately not all the API features I might like to use are in the 10.28 version that is in Ubuntu 10.04.  Since I don't intend to maintain a distribution, I need to target something as a lowest common denominator (it was Ubuntu 8.04 when I first started learning about gstreamer).

I'm still trying to decide if overall my problem is better solved by processing the video data by writing a plugin or using appsink & appsrc.  I'm playing around right now with both approaches, but straight off the top using appsink & appsrc lets me create my application with a simple make file instead of needing all the automake stuff to build a plug in.  Once I'd built the plugin template the first time,  "make" was all I needed afterwards, but I'd sure hate to have start with virgin Ubuntu install, and the one file I modified for my "plugin" and have to show someone else how to build and install it again!
 

[Kapil Agrawal]

I be more then happy to contribute.
While giving gstreamer training in my organization, I realised the best they understand when proper set of examples are given as assignment & if we make them understand concepts on this basis.

Also I think we need to make it very clear how do one debug, and understand the error, warnings etc in there application. People sometimes ask too ovious questions on irc, without even

cheers
- Kapil

On Fri, Nov 26, 2010 at 4:47 PM, Marco Ballesio <[hidden email]> wrote:

Hi,

On Thu, Nov 25, 2010 at 1:51 PM, Thomas Vander Stichele
<[hidden email]> wrote:
.. snip ..

>
> Who else is interested in writing part of a GStreamer book?

Networking for me, please!

Regards,
Marco

>
> Thomas
>
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twitter handle: @gst_kaps
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[Stefan Sauer]

Am 03.12.2010 21:36, schrieb wally_bkg:

>
>
> Sebastian Dröge-7 wrote:
>>
>> On Fri, 2010-12-03 at 09:09 -0800, wally_bkg wrote:
>>
>>> I also think the best documentation is a working sample code, with decent
>>> comments.  The only way I could figure out how to interpret video data
>>> pixels in a buffer (either as a plugin or appsink) was to stumble around
>>> the
>>> source code for gstgamma and gstvideoscale.  
>>>
>>> Of course the data you get in a buffer depends on the caps, but am I the
>>> only one who thinks there has to be a better way than:
>>>
>>> [...]
>>
>> For this you should use the libgstvideo API to get the video format,
>> width, height, rowstride, component widths/heights, component offsets,
>> pixel strides, etc. from the caps:
>> http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-libs/html/gst-plugins-base-libs-gstvideo.html
>>
>>
>
> Actually it was the nested function call to get the caps that seemed goofy
> to me.   I still need to do that on the buffer to use most of these API
> functions.

structure = gst_caps_get_structure (gst_buffer_get_caps(buf), 0);

well read the docs, and you'll see that caps can have multimple structure
entries (you specify 0 to get the first entry).

>
> Unfortunately not all the API features I might like to use are in the 10.28
> version that is in Ubuntu 10.04.  Since I don't intend to maintain a
> distribution, I need to target something as a lowest common denominator (it
> was Ubuntu 8.04 when I first started learning about gstreamer).

You can use the GStreamer developer PPA to have the latest releases on ubuntu.
https://launchpad.net/~gstreamer-developers/+archive/ppa

>
> I'm still trying to decide if overall my problem is better solved by
> processing the video data by writing a plugin or using appsink & appsrc.
> I'm playing around right now with both approaches, but straight off the top
> using appsink & appsrc lets me create my application with a simple make file
> instead of needing all the automake stuff to build a plug in.  Once I'd
> built the plugin template the first time,  "make" was all I needed
> afterwards, but I'd sure hate to have start with virgin Ubuntu install, and
> the one file I modified for my "plugin" and have to show someone else how to
> build and install it again!
>  

Maybe lets discuss this in a separate thread :)

Stefan

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