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gstreamer gstbasetransform

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Federico Paganini

gstreamer gstbasetransform

Hi,

I briefly explain to you my problem. For my thesis i am developing a gstreamer plug-in that encrypt an mpeg4 video with DES in CBC mode. The encryption is made frame by frame and because a frame doesn't contain an exact number of DES BLOCK SIZE(64 bit) i must padding the final bytes of the frame. Because i use padding the dimension of the frame in output is greater than that in input. For this reason i must allocate an output buffer of a precise size. So in the trasform function of my plug in i have tried to call this function: gst_base_transform_prepare_output_buffer( base, inbuf, newSize, inbuf->caps,&outbuf ); but when i try to compile i have this error:error: implicit declaration of function ‘gst_base_transform_prepare_output_buffer’ nevertheless i have done the include of gstbasetransform.h.
I would be very happy if you can say to me how i must to allocate an output buffer that is larger than input.

thanks

Best regards

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michael smith-6-3

Re: gstreamer gstbasetransform

On Sat, Jan 30, 2010 at 2:43 AM, Federico Paganini
<[hidden email]> wrote:

> Hi,
>
> I briefly explain to you my problem. For my thesis i am developing a
> gstreamer plug-in that encrypt an mpeg4 video with DES in CBC mode. The
> encryption is made frame by frame and because a frame doesn't contain an
> exact number of DES BLOCK SIZE(64 bit) i must padding the final bytes of the
> frame. Because i use padding the dimension of the frame in output is greater
> than that in input. For this reason i must allocate an output buffer of a
> precise size. So in the trasform function of my plug in i have tried to call
> this function: gst_base_transform_prepare_output_buffer( base, inbuf,
> newSize, inbuf->caps,&outbuf ); but when i try to compile i have this
> error:error: implicit declaration of function
> ‘gst_base_transform_prepare_output_buffer’ nevertheless i have done the
> include of gstbasetransform.h.
> I would be very happy if you can say to me how i must to allocate an output
> buffer that is larger than input.

For what you're doing, you probably don't want to make your element a
subclass of GstBaseTransform at all - instead you should directly
subclass GstElement. You can use gst_pad_alloc_buffer() or
gst_buffer_new_and_alloc() to allocate your output buffer with any
size you want.

Mike

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Federico Paganini

Re: gstreamer gstbasetransform

Hi Micheal,

i am following your advice in order to allocate the output buffer. But i have a problem, I insert my encryption plug-in in a pipeline and when i try to run the pipeline i obtain a file with only audio track; video track is disappeared. My pipeline is this:

                                      -->queue--->decoder--->audioconverter-->encoder--->identity--->queue--- AUDIO
Filesrc-->avidemux----                                                                                                                                ---> mux-->filesink
                                      -->queue--->DES TOOL--->queue------------------------------------------------------- VIDEO

I have annex in this mail my gst_destool_chain() function in which i have inserted the buffer output allocation and the encryption plug-in:
Can you say to me if is correct? Thanks in advance!!!!!

/* chain function
* this function does the actual processing
*/
static GstFlowReturn
gst_destool_chain (GstPad * pad, GstBuffer * inbuf)
{
GstDesTool *filter;
GstBuffer *outbuf;
outbuf=NULL;
filter = GST_DESTOOL (GST_OBJECT_PARENT (pad));
if (filter->silent == FALSE)
{
    //printf ("I'm plugged, therefore I'm in.\n");
    //filter->process (filter, GST_BUFFER_DATA (buf), GST_BUFFER_SIZE (buf));

    //Calculating the dimensione of the output buffer
        guint padSize = (8 - inbuf->size % 8);
        guint newSize = inbuf->size + padSize;
        guint pad;

    //Allocate output buffer
    outbuf= gst_buffer_new_and_alloc (newSize);
    GST_BUFFER_TIMESTAMP(outbuf)= GST_BUFFER_TIMESTAMP (inbuf);
    GST_BUFFER_DURATION(outbuf)= GST_BUFFER_DURATION (inbuf);
    gst_buffer_set_caps (outbuf, GST_PAD_CAPS (filter->srcpad));


    guint8 startCode[3] = { 0x00, 0x00, 0x01 };

    if ( (guint8*)memmem( inbuf->data, inbuf->size, startCode, 3 ) == inbuf->data )
    {
            memcpy( outbuf->data, inbuf->data, inbuf->size );

    // Doing padding
        for( pad = 0; pad < padSize; ++pad )
         {
            outbuf->data[ inbuf->size + pad ] = padSize;
         }
        // prepare des key
        DES_key_schedule schedule;
        DES_set_key ( (des_cblock*)filter->key, &schedule );
        //do encryption
        DES_ncbc_encrypt( inbuf->data + 4, outbuf->data + 4, newSize - 4, &schedule, (des_cblock*)filter->iv, DES_ENCRYPT );
    }
    else
    {
        fprintf( stderr, "begin of frame is not expected start code, dropping\n");
    }

}

/* just push out the incoming buffer without touching it */
gst_buffer_unref (inbuf);
return gst_pad_push (filter->srcpad, outbuf);
}

> Date: Sat, 30 Jan 2010 15:54:28 -0800
> From: [hidden email]
> To: [hidden email]
> Subject: Re: [gst-devel] gstreamer gstbasetransform
>
> On Sat, Jan 30, 2010 at 2:43 AM, Federico Paganini
> <[hidden email]> wrote:
> > Hi,
> >
> > I briefly explain to you my problem. For my thesis i am developing a
> > gstreamer plug-in that encrypt an mpeg4 video with DES in CBC mode. The
> > encryption is made frame by frame and because a frame doesn't contain an
> > exact number of DES BLOCK SIZE(64 bit) i must padding the final bytes of the
> > frame. Because i use padding the dimension of the frame in output is greater
> > than that in input. For this reason i must allocate an output buffer of a
> > precise size. So in the trasform function of my plug in i have tried to call
> > this function: gst_base_transform_prepare_output_buffer( base, inbuf,
> > newSize, inbuf->caps,&outbuf ); but when i try to compile i have this
> > error:error: implicit declaration of function
> > ‘gst_base_transform_prepare_output_buffer’ nevertheless i have done the
> > include of gstbasetransform.h.
> > I would be very happy if you can say to me how i must to allocate an output
> > buffer that is larger than input.
>
> For what you're doing, you probably don't want to make your element a
> subclass of GstBaseTransform at all - instead you should directly
> subclass GstElement. You can use gst_pad_alloc_buffer() or
> gst_buffer_new_and_alloc() to allocate your output buffer with any
> size you want.
>
> Mike
>
> ------------------------------------------------------------------------------
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> Choose flexible plans and management services without long-term contracts
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> _______________________________________________
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> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/gstreamer-devel

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Federico Paganini

Re: gstreamer gstbasetransform

Problem solved!!!

bye

From: [hidden email]
To: [hidden email]; [hidden email]
Date: Mon, 1 Feb 2010 11:51:59 +0100
Subject: Re: [gst-devel] gstreamer gstbasetransform

Hi Micheal,

i am following your advice in order to allocate the output buffer. But i have a problem, I insert my encryption plug-in in a pipeline and when i try to run the pipeline i obtain a file with only audio track; video track is disappeared. My pipeline is this:

                                      -->queue--->decoder--->audioconverter-->encoder--->identity--->queue--- AUDIO
Filesrc-->avidemux----                                                                                                                                ---> mux-->filesink
                                      -->queue--->DES TOOL--->queue------------------------------------------------------- VIDEO

I have annex in this mail my gst_destool_chain() function in which i have inserted the buffer output allocation and the encryption plug-in:
Can you say to me if is correct? Thanks in advance!!!!!

/* chain function
* this function does the actual processing
*/
static GstFlowReturn
gst_destool_chain (GstPad * pad, GstBuffer * inbuf)
{
GstDesTool *filter;
GstBuffer *outbuf;
outbuf=NULL;
filter = GST_DESTOOL (GST_OBJECT_PARENT (pad));
if (filter->silent == FALSE)
{
    //printf ("I'm plugged, therefore I'm in.\n");
    //filter->process (filter, GST_BUFFER_DATA (buf), GST_BUFFER_SIZE (buf));

    //Calculating the dimensione of the output buffer
        guint padSize = (8 - inbuf->size % 8);
        guint newSize = inbuf->size + padSize;
        guint pad;

    //Allocate output buffer
    outbuf= gst_buffer_new_and_alloc (newSize);
    GST_BUFFER_TIMESTAMP(outbuf)= GST_BUFFER_TIMESTAMP (inbuf);
    GST_BUFFER_DURATION(outbuf)= GST_BUFFER_DURATION (inbuf);
    gst_buffer_set_caps (outbuf, GST_PAD_CAPS (filter->srcpad));


    guint8 startCode[3] = { 0x00, 0x00, 0x01 };

    if ( (guint8*)memmem( inbuf->data, inbuf->size, startCode, 3 ) == inbuf->data )
    {
            memcpy( outbuf->data, inbuf->data, inbuf->size );

    // Doing padding
        for( pad = 0; pad < padSize; ++pad )
         {
            outbuf->data[ inbuf->size + pad ] = padSize;
         }
        // prepare des key
        DES_key_schedule schedule;
        DES_set_key ( (des_cblock*)filter->key, &schedule );
        //do encryption
        DES_ncbc_encrypt( inbuf->data + 4, outbuf->data + 4, newSize - 4, &schedule, (des_cblock*)filter->iv, DES_ENCRYPT );
    }
    else
    {
        fprintf( stderr, "begin of frame is not expected start code, dropping\n");
    }

}

/* just push out the incoming buffer without touching it */
gst_buffer_unref (inbuf);
return gst_pad_push (filter->srcpad, outbuf);
}

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