implement the Receive() fn:
HRESULT TransformFilter:: Receive(IMediaSample* pMediaSample)
{
HRESULT hr = S_OK;
do
{
hr = GetDeliveryBuffer(&pOutputSample);
if (FAILED(hr)) return hr;
hr = Transform(pSample,pOutputSample);
if(FAILED(hr)) return hr;
hr = m_pOutput->Deliver(pOutputSample);
pOutputSample->Release();
}while(nOutputSample != 0);
return hr;
}
>D:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\include\winnt.h(222) : error C2146: syntax error :
missing ';' before identifier 'PVOID64'
1>D:\Program Files\Microsoft Visual Studio
8\VC\PlatformSDK\include\winnt.h(222) : error C4430: missing type
specifier - int assumed. Note: C++ does not support default-int
1>D:\Program Files\Microsoft Visual Studio
8\VC\PlatformSDK\include\winnt.h(5940) : error C2146: syntax error :
missing ';' before identifier 'Buffer'
1>D:\Program Files\Microsoft Visual Studio
8\VC\PlatformSDK\include\winnt.h(5940) : error C4430: missing type
specifier - int assumed. Note: C++ does not support default-int
1>D:\Program Files\Microsoft Visual Studio
8\VC\PlatformSDK\include\winnt.h(5940) : error C4430: missing type
specifier - int assumed. Note: C++ does not support default-int
Solution:
-----------
include the following macro in the the Winnt.h before the following lines
typedef void *PVOID;
typedef void *POINTER_64 PVOID64;
After code change:
#define POINTER_64 __ptr64
typedef void *PVOID;
typedef void *POINTER_64 PVOID64;
AnotherSolution:
====================
Update BaseTsd.h with latest platform SDk file.
returns the "No combination of intermediate filters found"
Observation:
if we connected the Mpeg1 Encoder that is connecting pins in the
RenderStream as follows:
hr = CaptureGraphBuilder2->RenderStream(
NULL,NULL,SourceFilter,mpeg1VideoDecoder,Mpeg4Encoder);
( Source FIlter might be AddSourceFilter() with URL).
RenderStream is running successfully.
Solution:
============
hr = CaptureGraphBuilder2->RenderStream(
NULL,&MEDIATYPE_Video,mp4Source,mpeg4videoDecoder,Mpeg4Encoder);
if we modified it as follows: it is working fine...
The Reason is RenderStream() media type is NULL means it will
directly connects the Source Filter's First Pin the Video Decoder
Filter.
In case of MPEG1 Source Filter, the First output pin is video so it
is running successfully without any problem.
In case of MP4 Source Filter failure case, First output pin is audio
Pin. So the RenderStream() tries to connect with MP4 Source Audio
output pin with Video decoder. So that causes the error.
if we specified the MediaType as video, RenderStream() will takes the
Source Filter's Video output pin and tries to connect it with video
decoder. So it is working fine...
mDurationInSecs = pMediaTrkInfo->trackDuration / lMovieInfo.timescale;
fFrameRate = pMediaTrkInfo->totalNumOfFrames/ (*apVidInfoLst)[index].mDurationInSecs;
//Frame Rate calculation if 10 frames r played in 2 secs, then FPS is 5 (10/5)Error C2146: syntax error: missing ';' before identifier PVOID64
VS 2005 error with Dshow baseclasses.
C:\Program Files\Microsoft Visual Studio 8\VC\PlatformSDK\include\winnt.h(222) : error
C2146: syntax error : missing ';' before identifier 'PVOID64'
Solution:
--------------
The DirectX Include directory contains an early version of BaseTsd.h which does not
include the definition for POINTER_64. You should instead use the version of BaseTsd.h in
the Platform SDK, either the one that ships with Visual Studio 2005 (C:\Program
Files\Microsoft Visual Studio 8\VC\PlatformSDK\Include\BaseTsd.h) or in an updated
Microsoft SDK installation. In order to get the compiler to use the right file, just
remove BaseTsd.h from the DirectX Include directory.
1.Quicktime, mp4,3gp file having hint track can be transferred thru http or ftp protocols
2.Moov atom index must be at the beginning of the file ... so that player can play the file before downloading the entire content...
3.Self contained movie can be streamable...
Solutions:
-----------
Any Quicktime,mp4 or 3gp files can be able to do Progressive Download Streaming
if moov atom is @ first..Moov atom index must be at the beginning of the file ... so that player can play the file before downloading the entire content.
For Example
3gp file atoms are like this:
------------------------------
ftyp
moov
mdat
we can stream it in PD streaming.
if the 3gp atoms are as follows:
ftyp
mdat
moov
this indicates Moov atom is at the end of the file... So it can't be streamable in Progressive Download.
PD Stack:
-----------
within PD stack,we will wait for the File Size and information about the video and audio track info...
if it doesnt receive the video, audio track info and file information it will not proceed to download the content.
Without calling Pause () fn we are not able to set seek position...
--------------------------------------------------------------------------
we are able to do the SetPosition ( set the seek position) on the fly while running the video.
In our Source Filter we are not able to set the seek position. Before setting the seek position, we have to the
following:
Pause() of IMediaControl;
SetPosition();
Run()
then only we are able to set the seek position to the source filter.
Solution:
--------------
The reason we are not able to do the seek position while running the video is we are not handling
setPosition properly.
if Source Filter's output pin thread exists , that represents the video is running; then
i)call the stop on Source Filter's output pins .
if(m_paStreams[i]->ThreadExists())
{
if(m_paStreams[i]->IsConnected())
{
hr = m_paStreams[i]->DeliverBeginFlush() ;
}
if(m_State != State_Stopped )
{
hr = m_paStreams[i]->Stop();
}
if(m_paStreams[i]->IsConnected())
{
hr = m_paStreams[i]->DeliverEndFlush() ;
}
}
ii)Set the seek position
iii)call the Pause () fn on Each output pins of the source Filter
If the filter graph is stopped, the video renderer does not update the image after a seek operation. To the user, it will
appear as if the seek did not happen. To update the image, pause the graph after the seek operation. Pausing the graph cues a
new video frame for the video renderer. You can use the IMediaControl::StopWhenReady method, which pauses the graph and then
stops it.
H.264 Nonstandard clip Crash issue in Quicktime 7.0.3 :
=========================================================
i) Normally the width and height of the H.264 will be the multiple of 16.
ii)Non standard clip means it will not be the multiple of 16,like 450x360
iii)In Quicktime Player,Quicktime File parser will give original width and height
( 450x360) and the decoder allocated the output video width and height as
450 *360. This will leads to crash. Decoder must output the buffer as follows
464 * 364; (width and height are aligned as multiple of 16).
In H264, we will encode the video frame with 100x100 and the width and height may
be the 112 * 112; the actual video width height is as 100,100.
iv)if the decoder allocates only the 450* 360 output width the crash might happen
in decoder or the renderer which renders the data;
Quicktime may solved this issue in latest version Quicktime 7.5. In older
version,they may allocate the output width and height as 450*360 and crashed.
Our decoder too behaved in the same way.
Why WMP calls the IFileSourceFilter's Load fn Twice:
-----------------------------------------------------------
if we implemented the IFileSourceFilter in our Filter, WMP calls the IFileSourceFilter's Load() function twice;
Reason:
----------
WMP calls "Load" two times, First time just to check whether the filter is proper dll or not
WMP call "Load" again for the second time. Second time only we have to create any pins to the Filter;
In case of Source Filter,we will be creating pins only at the second time;
WMP player is not loading the Filter DLL in Wifi :
-------------------------------------------------------------------------
1.We enabled the Wifi in a mobile device;
Thru the Wifi, we try to reach the server for streaming server;
We are giving the rtsp/PD server address in WMP;
In WMP, if we specified the http or rtsp, WMP must automatically load the
Filter.
But it doesnt happen and our filter is not getting loaded;
Reason:
----------
WMP player will not load the filter DLL before checking the host.
WMP Behavior:
-------------
WMP will sends some form of HTTP GET / some requests to server
For Example rtsp://10.203.92.78:8080/1.3gp
WMP will sends the some network request to the the 10.203.92.78 server; if the
server acknowledges the WMP, then only WMP tries to load the filter DLL for the
corresponding format;
In case of the Wifi, it may sends the HTTP Get command. Wifi server may not
response to the request or some form of communication gap happens.. so WMP will not get
the response;
Solution:
==========
Develop our own player application to insert the Streaming source Filter and render
Note:
-------
if our Player application is using RenderFile() means that might cause the same problem;
Problem :
------------
Issues in RTSP/LiveStream Audio and video sync
RTSP video on Demand videos are playing fine. But Only Livestream audio and video
sync is not happening Streaming server is sending RTSP as meta data channel( just for DESCRIBE,
PLAY,PAUSE and TEARDOWN commands);Streaming server will send video and audio data over the
RTP.
Analysis:
----------
if there is any issue in audio and video sync issues in RTSP/Livestream RTSP,
it is because of the Streaming Server.
rtsp streaming servers are specialized servers;They have to do audio and video
sync; In case of rtsp streaming, it is enough to render the audio and video data using the
RTP timestamp. there is no need to do audio video sync with RTCP.if we are doing RTCP
sync, that will be better;
But For RTCP sync timestamp calculation it will takes much time because of
floating operations involved in it. So In case of low end devices such as mobile they will
not use the RTCP for sync; it is enough to do render the video and audio with RTP
timestamp;
Solution:
----------
Make the Streaming server to give output as video and audio synchronized;
IE internet browsing problem in Windows Mobile:
---------------------------------------------------------------------
1.Even though I configured the proxy server and USB setting as Turbo Mode.
I am not able to open any web pages in a mobile.
Solution:
----------
I have opened Active Sync's connection Settings in PC and selected the automatic from the list of options in combo box.
The computer is connected to:
Automatic
Work Network
Internet
it was "Work Network" previously. I modified it to the "Automatic" in a PC then the web pages are able to open in IE.
WinCE Deployment error:
------------------------------------------
Deployment and/or registration failed with error: 0x8973190e. Error writing file '\Program Files\VideoRenderer.dll'. Error 0x80450001: (null)
========== Build: 0 succeeded, 0 failed, 3 up-to-date, 0 skipped ==========
========== Deploy: 2 succeeded, 1 failed, 0 skipped ==========
This is due to I have deployed the DLL in Windows folder But the mobile is not allowing to deploy...
So I prepared the cab ( will have the DLL) and install it in mobile.
But it is also not working...
The problem is Bulverde device shown error as the Problem occurred in tmarshaller.exe file.
Reason:
----------------
Previously I got the same error when Codec DLL is missing in the Codec Filter.
if I deployed it, then I got the error...
I have opened the file
using fopen() fn in Constructor of a video renderer... It causes the problem.
if I opened the file in SetMediaType() fn I didnt get any errors...
So Beware of Fopen() calls...
I have declared the public variable in CVideoRenderer and opened the fopen("\\My Documents\\test.log"); in the CVideoRenderer's constructor...
CVideoRenderer's constructor will be called in the CreateInstance of IUnknown implementation of a filter...
This is the General problem to any COM DLL.
How to configure the VS 2005 wizard to create the .rel file:
----------------------------------------------------------------------------------------
Projects-> Properties->Linker ->CommandLine
/subsystem:windowsce,5.01 /machine:THUMB /savebaserelocations:"$(TargetDir)$(TargetName).rel"
Windows mobile is a general term for Windows OS that are used in handheld devices.
For Example Windows OS is a general term... Under this category we are having different flavors like Windows 98,windows XP,
Windows NT and so on.
Windows Mobile operating system for handhelds:
1.Pocket PC Edition
2.Pocket PC Phone Edition, and
3.Smartphone Edition
Pocket PC Edition:
--------------------
Stand-alone PDAs, such as the Dell Axim X51 series and the HP iPaq rx1950, use Pocket PC Edition and come with the
full Mobile Office suite, including Word Mobile, Excel Mobile,and PowerPoint Mobile. These handhelds typically have
240x320-pixel touch screens, can feature wireless connectivity, and are best for those who want a palm-size device to
organize vital information with the option to work on the go and surf the Web.
( it is like a handheld PC )
Pocket PC Phone Edition:
------------------------
Devices that run Pocket PC Phone Edition are similar to Pocket PC PDAs in shape and size (including the touch-screen
functionality), with the full suite of office apps, but they add cellular-wireless capabilities so that you can make phone
calls. These all-in-one mobiles are good for power users who need the full functionality of being able to work and stay
connected on the road. Examples of Pocket PC phones are the Palm Treo 700w.
SmartPhone:
-------------
Windows Mobile Smartphone Edition offers the biggest difference of the three versions. First, the mobiles are
smaller, resembling cell phones, and they generally feature 320x240-pixel displays that aren't touch sensitive. Instead, you
navigate via soft keys and a joystick. Also, while you get all the calendar and contact tools, you don't get the entire
Office Mobile suite, just Outlook Mobile; third-party apps, such as Westtek's ClearVue Suite, are available so that you can
view work documents. These types of smart phones are perfect for users who want the phone form factor but also want to stay
up-to-date and be more productive on the road.
Major Difference between Smartphone and Pocket PC:
SmartPhone is a low cost solution compare to Pocket PC.
Touch screen facility available in Pocket PC.Smartphone will not have touch screen facility.we have to navigate via softkeys or joystick.
That is it...
Mp4UI tool is an open source file. Many converters are not properly converting the meta data. For Example, If I am converting the video from WMV to MP4 , the meta data available in a WMV is not available in ConvertedMP4 file;
So we can make use of the MP4UI tool to add meta data to the MP4 file;
MP4UI dialog:
Click New/Open button and select MP4 file;
Look at the Lower Right corner, it is having M symbol Just click on this;
After Entering all these information and enable the Part of a compilation check box and Click on OK; it will add the Meta data to the MP4 file;
Using this Metadata, we can know the artist, composer, Singer, Film and so on information about the media file;
Camera Driver Pin resolution problem:
---------------------------------------------------------
1.Capture pin resolutions must be supported in Preview Pin Resolution;
if Capture Pin resolutions are not matched with the Preview Pin Resolution;
Cause:
--------
This is the bug in camera or capture driver;Capture Pin resolution must be supported in Preview Pin resolution;
windows media player Seek Bar will not work for video having less than 1 second duration?:
-------------------------------------------------------------------------------------------
We checked whether the windows media player will not display the seek bar properly for video having less than 1 second duration;We recorded the wmv video using PIMG with less than 1 second; it is playing fine in media player;
within Motorola cell, we hard reset the device; By default it is having wmv recording;
and recorded the file for testing this scenario;
While developing an application in VS2005,
I faced the problem in viewing Output Window; Even though
I have selected View -> Output, that doesnt display the Output Window;
Solution :
-----------
Window-> Reset window layout Now Click the View-> Output displays the
Output window;
Note:
----------
Not Only for Output Window, we can use the same approach for all
windows available in VS 2005.
Capture Pin -> Video Encoder -> Muxer filter
Normally preview pin will render the video; Capture Pin Stream is
stopped using ControlStream() fn;
whenever the "Start Recording" button was pressed then we need to
Start the capture Pin Stream;
In other words we need to Captured video data to be written into media
file as well as to be rendered on screen;
For doing this, we will connect the filters as follows:
Video Capture Pin -> Video Encoder->Muxer
Audio Capture Pin ->Audio Encoder->Muxer
video Preview pin -> Video Renderer;
Until the user gives "Start Recording" command, we need to Stop the
Stream in Video capture and Audio Capture pin;
we need to Start them only when the user gives "Start Recording";
if No media file was recorded, then during the connection itself the
muxer filter will creates an empty file;
we need to delete it ; if No media file was recorded, then the current
filename is to be deleted from the file system;
This is what we have done ;
m_pCaptureGraphBuilder2->ControlStream //Stop the capture Pin
(
&PIN_CATEGORY_CAPTURE,
&MEDIATYPE_Video,
m_pVideoCaptureFilter,
&rtStart,
&rtStop,1,2
);
ControlStream of Live Source will do the Start and Stop of the Stream;
0,MAXLONGLONG - To Start the Stream
MAXLONGLONG,0 - To Stop the Stream;
Problem :
----------
1. I have Stopped the Capture Pin and Started the Preview Pin using
ControlStream() fn;
it gives the Black rectangle instead of rendering video;
Solution;
---------
I have deeply analyzed the Stream;
Reason for the problem is I have not Started the MediaControl using
Run() method;
if I called the IMediaControl's Run() method it works fine;
HRESULT StartPreview()
{
HRESULT hr = S_OK;
REFERENCE_TIME rtPreviewStart = 0,rtPreviewStop = MAXLONGLONG;
REFERENCE_TIME rtStart, rtStop;
rtStart = MAXLONGLONG;
rtStop = 0;
hr = m_pCaptureGraphBuilder2->ControlStream //Stop the capture Pin
(
&PIN_CATEGORY_CAPTURE,
&MEDIATYPE_Video,
m_pVideoCaptureFilter,
&rtStart,
&rtStop,1,2
);
if(FAILED(hr))
{
printf("\n VideoControlStream() Stop Failure Error Code:%x",hr);
return hr;
}
//Start the Preview Stream
hr = m_pCaptureGraphBuilder2->ControlStream( &PIN_CATEGORY_PREVIEW,
&MEDIATYPE_Video,
m_pVideoCaptureFilter,
&rtPreviewStart, // Start now.
&rtPreviewStop, // (Don't care.)
3,4
);
if(FAILED(hr))
{
printf("\n ControlStream() fn Error : %x",hr);
return hr;
}
hr = m_pCaptureGraphBuilder2->ControlStream( &PIN_CATEGORY_CAPTURE,
&MEDIATYPE_Audio,
m_pAudioCaptureFilter,
&rtStart, // Start now.
&rtStop, // (Don't care.)
5,6
);
if(FAILED(hr))
{
printf("\n Audio ControlStream() Stop Failure Error Code:%x",hr);
return hr;
}
}
if(m_pMediaControl)
{
m_pMediaControl->Run();
}
return hr;
}
RenderStream() fn executed without giving any problem for the first
time; During the second time, RenderStream() fn I got an error as
E_FAIL
Solution:
------------------
1.CLSID_VideoCapture ( Video Source Filters CoCreateInstance
must be called only once in a program otherwise we will get
RenderStream() fn failure error;
whenever we reconstruct the filter graphs by releasing filters in a
filter graph.
2.But For VideoCapture source filter we need to create the
object (using CoCreateInstance) and we have to use that object thru
out the application.
otherwise we will get RenderStream() fn failure message;
Image Stride
When a video image is stored in memory, the memory buffer might contain extra padding bytes after each row of pixels. The padding bytes affect how the image is stored in memory, but do not affect how the image is displayed.
The stride is the number of bytes from one row of pixels in memory to the next row of pixels in memory. Stride is also called pitch. If padding bytes are present, the stride is wider than the width of the image, as shown in the following illustration.
Two buffers that contain video frames with equal dimensions can have two different strides. If you process a video image, you must take the stride into account.
In addition, there are two ways that an image can be arranged in memory. In a top-down image, the top row of pixels in the image appears first in memory. In a bottom-up image, the last row of pixels appears first in memory. The following illustration shows the difference between a top-down image and a bottom-up image.
A bottom-up image has a negative stride, because stride is defined as the number of bytes need to move down a row of pixels, relative to the displayed image. YUV images should always be top-down, and any image that is contained in a Direct3D surface must be top-down. RGB images in system memory are usually bottom-up.
Video transforms in particular need to handle buffers with mismatched strides, because the input buffer might not match the output buffer. For example, suppose that you want to convert a source image and write the result to a destination image. Assume that both images have the same width and height, but might not have the same pixel format or the same image stride.
The following example code shows a generalized approach for writing this kind of function. This is not a complete working example, because it abstracts many of the specific details.
Copy Code
void ProcessVideoImage(
BYTE* pDestScanLine0,
LONG lDestStride,
const BYTE* pSrcScanLine0,
LONG lSrcStride,
DWORD dwWidthInPixels,
DWORD dwHeightInPixels
)
{
for (DWORD y = 0; y < dwHeightInPixels; y++)
{
SOURCE_PIXEL_TYPE *pSrcPixel = (SOURCE_PIXEL_TYPE*)pDestScanLine0;
DEST_PIXEL_TYPE *pDestPixel = (DEST_PIXEL_TYPE*)pSrcScanLine0;
for (DWORD x = 0; x < dwWidthInPixels; x +=2)
{
pDestPixel[x] = TransformPixelValue(pSrcPixel[x]);
}
pDestScanLine0 += lDestStride;
pSrcScanLine0 += lSrcStride;
}
}
This function takes six parameters:
A pointer to the start of scan line 0 in the destination image.
The stride of the destination image.
A pointer to the start of scan line 0 in the source image.
The stride of the source image.
The width of the image in pixels.
The height of the image in pixels.
The general idea is to process one row at a time, iterating over each pixel in the row. Assume that SOURCE_PIXEL_TYPE and DEST_PIXEL_TYPE are structures representing the pixel layout for the source and destination images, respectively. (For example, 32-bit RGB uses the RGBQUAD structure. Not every pixel format has a pre-defined structure.) Casting the array pointer to the structure type enables you to access the RGB or YUV components of each pixel. At the start of each row, the function stores a pointer to the row. At the end of the row, it increments the pointer by the width of the image stride, which advances the pointer to the next row.
This example calls a hypothetical function named TransformPixelValue for each pixel. This could be any function that calculates a target pixel from a source pixel. Of course, the exact details will depend on the particular task. For example, if you have a planar YUV format, you must access the chroma planes independently from the luma plane; with interlaced video, you might need to process the fields separately; and so forth.
To give a more concrete example, the following code converts a 32-bit RGB image into an AYUV image. The RGB pixels are accessed using an RGBQUAD structure, and the AYUV pixels are accessed using a DXVA2_AYUVSample8 Structure structure.
Copy Code
//-------------------------------------------------------------------
// Name: RGB32_To_AYUV
// Description: Converts an image from RGB32 to AYUV
//-------------------------------------------------------------------
void RGB32_To_AYUV(
BYTE* pDest,
LONG lDestStride,
const BYTE* pSrc,
LONG lSrcStride,
DWORD dwWidthInPixels,
DWORD dwHeightInPixels
)
{
for (DWORD y = 0; y < dwHeightInPixels; y++)
{
RGBQUAD *pSrcPixel = (RGBQUAD*)pSrc;
DXVA2_AYUVSample8 *pDestPixel = (DXVA2_AYUVSample8*)pDest;
for (DWORD x = 0; x < dwWidthInPixels; x++)
{
pDestPixel[x].Alpha = 0x80;
pDestPixel[x].Y = RGBtoY(pSrcPixel[x]);
pDestPixel[x].Cb = RGBtoU(pSrcPixel[x]);
pDestPixel[x].Cr = RGBtoV(pSrcPixel[x]);
}
pDest += lDestStride;
pSrc += lSrcStride;
}
}
The next example converts a 32-bit RGB image to a YV12 image. This example shows how to handle a planar YUV format. (YV12 is a planar 4:2:0 format.) In this example, the function maintains three separate pointers for the three planes in the target image. However, the basic approach is the same as the previous example.
Copy Code
void RGB32_To_YV12(
BYTE* pDest,
LONG lDestStride,
const BYTE* pSrc,
LONG lSrcStride,
DWORD dwWidthInPixels,
DWORD dwHeightInPixels
)
{
assert(dwWidthInPixels % 2 == 0);
assert(dwHeightInPixels % 2 == 0);
const BYTE *pSrcRow = pSrc;
BYTE *pDestY = pDest;
// Calculate the offsets for the V and U planes.
// In YV12, each chroma plane has half the stride and half the height as the Y plane.
BYTE *pDestV = pDest + (lDestStride * dwHeightInPixels);
BYTE *pDestU = pDest + (lDestStride * dwHeightInPixels) + ( (lDestStride * dwHeightInPixels) / 4 );
// Convert the Y plane.
for (DWORD y = 0; y < dwHeightInPixels; y++)
{
RGBQUAD *pSrcPixel = (RGBQUAD*)pSrcRow;
for (DWORD x = 0; x < dwWidthInPixels; x++)
{
pDestY[x] = RGBtoY(pSrcPixel[x]); // Y0
}
pDestY += lDestStride;
pSrcRow += lSrcStride;
}
// Convert the V and U planes.
// YV12 is a 4:2:0 format, so each chroma sample is derived from four RGB pixels.
pSrcRow = pSrc;
for (DWORD y = 0; y < dwHeightInPixels; y += 2)
{
RGBQUAD *pSrcPixel = (RGBQUAD*)pSrcRow;
RGBQUAD *pNextSrcRow = (RGBQUAD*)(pSrcRow + lSrcStride);
BYTE *pbV = pDestV;
BYTE *pbU = pDestU;
for (DWORD x = 0; x < dwWidthInPixels; x += 2)
{
// Use a simple average to downsample the chroma.
*pbV++ = ( RGBtoV(pSrcPixel[x]) +
RGBtoV(pSrcPixel[x + 1]) +
RGBtoV(pNextSrcRow[x]) +
RGBtoV(pNextSrcRow[x + 1]) ) / 4;
*pbU++ = ( RGBtoU(pSrcPixel[x]) +
RGBtoU(pSrcPixel[x + 1]) +
RGBtoU(pNextSrcRow[x]) +
RGBtoU(pNextSrcRow[x + 1]) ) / 4;
}
pDestV += lDestStride / 2;
pDestU += lDestStride / 2;
// Skip two lines on the source image.
pSrcRow += (lSrcStride * 2);
}
}
In all of these examples, it is assumed that the application has already determined the image stride. You can sometimes get this information from the media buffer. Otherwise, you must calculate it based on the video format. For more information about calculating image stride and working with media buffers for video, see Uncompressed Video Buffers.
