Need clarification on gstcolorbalance

[Yogesh Marwaha]

Hi,

I'm trying to add options of contrast, brightness etc. in my app.
GStreamer's videobalance and xvimagesink elements support
GstColorBalance interface. But in case of xvimagesink, I'm unable
to get a list of channels.

Following is the code snippet I'm using: -

    GstElement *a = gst_element_factory_make("xvimagesink",
"gravity-playbin-video-a");
    if(GST_IS_COLOR_BALANCE(a)){
        qDebug() << "Color balance.";
        const GList * channels =
gst_color_balance_list_channels(GST_COLOR_BALANCE(a));
        if(!channels)
            qDebug() << "Channels is null.";
        while ( channels ) {
            qDebug() << "Channel name:" <<
GST_COLOR_BALANCE_CHANNEL(channels->data)->label;;
            channels = g_list_next(channels);
        }
    }else{
        qDebug() << "No color balance.";
    }

    GstElement *b = gst_element_factory_make("videobalance",
"gravity-playbin-video-b");
    if(GST_IS_COLOR_BALANCE(b)){
        qDebug() << "Color balance.";
        const GList * channels =
gst_color_balance_list_channels(GST_COLOR_BALANCE(b));
        if(!channels)
            qDebug() << "Channels is null.";
        while ( channels ) {
            qDebug() << "Channel name:" <<
GST_COLOR_BALANCE_CHANNEL(channels->data)->label;;
            channels = g_list_next(channels);
        }
    }else{
        qDebug() << "No color balance.";
    }


Here is the output: -
Color balance.
Channels is null.
Color balance.
Channel name: "HUE"
Channel name: "SATURATION"
Channel name: "BRIGHTNESS"
Channel name: "CONTRAST"


What could be the cause of problem? How should I do it properly?

Regards,

Yogesh Marwaha
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[Tim-Philipp Müller-2]

On Sun, 2012-05-20 at 13:17 +0530, Yogesh Marwaha wrote:

> Hi,
>
> I'm trying to add options of contrast, brightness etc. in my app.
> GStreamer's videobalance and xvimagesink elements support
> GstColorBalance interface. But in case of xvimagesink, I'm unable
> to get a list of channels.
>
> Following is the code snippet I'm using: -
>
>     GstElement *a = gst_element_factory_make("xvimagesink",
> "gravity-playbin-video-a");
>     if(GST_IS_COLOR_BALANCE(a)){
>  (...)
> What could be the cause of problem? How should I do it properly?

Try adding a

  gst_element_set_state (a, GST_STATE_READY);

right after creating it.

Cheers
 -Tim

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[Yogesh Marwaha]

On 20 May 2012 16:38, Tim-Philipp Müller <[hidden email]> wrote:

> On Sun, 2012-05-20 at 13:17 +0530, Yogesh Marwaha wrote:
>> Hi,
>>
>> I'm trying to add options of contrast, brightness etc. in my app.
>> GStreamer's videobalance and xvimagesink elements support
>> GstColorBalance interface. But in case of xvimagesink, I'm unable
>> to get a list of channels.
>>
>> Following is the code snippet I'm using: -
>>
>>     GstElement *a = gst_element_factory_make("xvimagesink",
>> "gravity-playbin-video-a");
>>     if(GST_IS_COLOR_BALANCE(a)){
>>  (...)
>> What could be the cause of problem? How should I do it properly?
>
> Try adding a
>
>  gst_element_set_state (a, GST_STATE_READY);
>
> right after creating it.

Now I get the following:-
Channel name: XV_BRIGHTNESS
Channel name: XV_CONTRAST

I was also expecting HUE and SATURATION to be listed.

Anyways, my main problem is that values of these properties provided
by xvimagesink & videobalance elements are imcompatiable, so I was
searching for a standard way of setting their values so that I may use
same code, no matter I'm using xvimagesink or videobalance+ximagesink.

What do you recommend? Would I have to/(Should I) use separate code
for both cases? Or do I forget that xvimagesink offers these
properties?

PS: Upto now I had been thinking that standard property names in
gstreamer (e.g. the volume property) imply standard values, and all my
code also assumes that.

Regards,

Yogesh Marwaha
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