Delphi OpenH264 decode

[randydom]

Hello , i'm using the cisco OpenH264 codec in coding and decoding process , the coding stage works very well and i can read my encoded H.264 file correctly , the issue is with my decoding process and mainly the conversion from I420 to ARGB , please can any one helps to fix this .

Here's my Decoding function ( from the OpenH264 wrapper DLL ) :

/*
* [ IN ]   SourceData : the encoded frame(s)
* [ OUT ] pTargetbuffer : the Target buffer 
* [ OUT ] width
* [ OUT ] height
*/
int H264Decoder_decode(BufferedData &SourceData, void *pTargetbuffer, int *width, int *height) {

 	int iStride[2];
	init();

         ... the decoding routine : pData contains the YUV 

        if (ret != dsErrorFree) {

			return -1;
		}
		if (!m_sBufferInfo.iBufferStatus) {
			return -2;
		}

        LWidth = m_sBufferInfo.UsrData.sSystemBuffer.iWidth;
	LHeight = m_sBufferInfo.UsrData.sSystemBuffer.iHeight;
	*width = LWidth;
	*height = LHeight;

	  iStride[0] = m_sBufferInfo.UsrData.sSystemBuffer.iStride[0];
	  iStride[1] = m_sBufferInfo.UsrData.sSystemBuffer.iStride[1];
			   
               /*
		BOOL I420ToARGB(const unsigned char *src_y, int src_stride_y,
                const unsigned char *src_u, int src_stride_u,
                const unsigned char *src_v, int src_stride_v,
                unsigned char *dst_frame, int dst_stride_frame,
                int width, int height);
		*/

		I420ToARGB(
		(unsigned char *)pData[0],iStride[0],
		(unsigned char *)pData[1],iStride[1],
		(unsigned char *)pData[2],iStride[1],
		(unsigned char *)pTargetbuffer,
                /*
                * if i put LWidth*4 which is the correct way to get the real pixel i get an AV in delphi
                * and i think the AV is not related to delphi but the OpenH264 itself
                */
		LWidth*2,
		LWidth,LHeight);
			
		return 0;
}

and here's my Delphi implementation :

  Image.Picture.Bitmap.PixelFormat := pf24bit;
  Image.Picture.Bitmap.Width  := 320;
  Image.Picture.Bitmap.Height := 240;
...
Result:=H264Decoder_decode(FEncodedBuffer,
                        Image.Picture.Bitmap.ScanLine[Image.Picture.Bitmap.Height-1],
                        EncodedBufferSize,LWidth,LHeight); 
						
if result=0 then Image.Repaint;

So many thanks .
yours,Randy

[pandy]

If i understand correctly your problem then I420 use 12 bits per pixel (U and V are 1/4 size each of the Y plane size), ARGB use 32 bits per pixel. before converting YUV (or correctly YCbCr) you should upscale plane U and V to size of plane Y (this sampling scheme is called 4:4:4). A is Alpha plane and it doesn't exist in your YUV source so you need to create it as empty table filled with constant.
If i misunderstood your problem then sorry.

[randydom]

If i understand correctly your problem then I420 use 12 bits per pixel (U and V are 1/4 size each of the Y plane size), ARGB use 32 bits per pixel. before converting YUV (or correctly YCbCr) you should upscale plane U and V to size of plane Y (this sampling scheme is called 4:4:4). A is Alpha plane and it doesn't exist in your YUV source so you need to create it as empty table filled with constant.
If i misunderstood your problem then sorry.

so many thanks pandy , can you just give me this step ( in code if possible ) .

[randydom]

so many thanks i've fixed it , the issue was that i used :

Image.Picture.Bitmap.PixelFormat := pf24bit;

but the correct PixelFormat is :

PixelFormat is the pf32bit

Thank you again

[jagabo]

http://fourcc.org/pixel-format/yuv-i420/
https://www.fourcc.org/fccyvrgb.php