How to read an specified frame from an MPEG-TS video file?

[Yashil]

Marcus Nascimento wrote
> Hi Yashil,
> 
> I'm very interested in this solution too.
> I believe you are a bit ahead of me.
> Please, let me know if you find a good solution.
> 
> If I manage to do it, I'll let you know.
> 
> Thanks very much,
> Marcus

Here is my sample code. It grabs two frames from given video file and
displays it by opencv. The first frame seek is done by given frame number
and the second frame seek is done by given time position. It works for
several codecs in my tests but I have not been able to make it work for
mpeg2-ts files yet.

MyGstFrameCap1.cpp

/**********************************************************************/
// gstreamer includes and libraries
#include <gst/gst.h>
#include <gst/app/gstappsink.h>
#pragma comment( lib, "gstreamer-1.0.lib" )
#pragma comment( lib, "glib-2.0.lib" )
#pragma comment( lib, "gobject-2.0.lib" )
#pragma comment( lib, "gstapp-1.0.lib" )

/**********************************************************************/
// opencv includes and libraries
#include <opencv2/opencv.hpp>
#ifdef _DEBUG
#pragma comment( lib, "comctl32" )
#pragma comment( lib, "opencv_core246d" )
#pragma comment( lib, "opencv_highgui246d" )
#ifndef _DLL
#pragma comment( lib, "zlibd" )
#pragma comment( lib, "IlmImfd" )
#pragma comment( lib, "libjasperd" )
#pragma comment( lib, "libjpegd" )
#pragma comment( lib, "libpngd" )
#pragma comment( lib, "libtiffd" )
#endif
#else
#pragma comment( lib, "comctl32" )
#pragma comment( lib, "opencv_core246" )
#pragma comment( lib, "opencv_highgui246" )
#ifndef _DLL
#pragma comment( lib, "zlib" )
#pragma comment( lib, "IlmImf" )
#pragma comment( lib, "libjasper" )
#pragma comment( lib, "libjpeg" )
#pragma comment( lib, "libpng" )
#pragma comment( lib, "libtiff" )
#endif
#endif

/**********************************************************************/
void MyfCopyRGBbuf2CvMat( cv::Mat& oMatFrameInp, unsigned char *pDataInp )
{
	int nDi = 0;
	for( int nRi = 0; nRi < oMatFrameInp.rows; nRi++ )
	{
		for( int nCi = 0; nCi < oMatFrameInp.cols; nCi++ )
		{
			oMatFrameInp.data[oMatFrameInp.step[0] * nRi + oMatFrameInp.step[1] * nCi
+ 2] = pDataInp[nDi++]; // R
			oMatFrameInp.data[oMatFrameInp.step[0] * nRi + oMatFrameInp.step[1] * nCi
+ 1] = pDataInp[nDi++]; // G
			oMatFrameInp.data[oMatFrameInp.step[0] * nRi + oMatFrameInp.step[1] * nCi
+ 0] = pDataInp[nDi++]; // B
		}
	}
}

/**********************************************************************/
void MyfDispGstSampleInOpenCvWin( GstSample *pstGstSampleInp, gchar
*szgWinTitle )
{
	if( !pstGstSampleInp ) { g_print( "*** Error: Could not make snapshot (may
be due to eos)."); return; }

	GstCaps *pstGstCaps1;
	pstGstCaps1 = gst_sample_get_caps( pstGstSampleInp );
	if( !pstGstCaps1 ) { g_print( "*** Error: gst_sample_get_caps fails to get
sample cpas." ); return; }

	GstStructure *pstGstSt1;
	pstGstSt1 = gst_caps_get_structure( pstGstCaps1, 0 );

	gint nFrameWidth, nFrameHeight;
	gboolean nGboolRes1;
	nGboolRes1 = gst_structure_get_int( pstGstSt1, "width", &nFrameWidth );
	nGboolRes1 |= gst_structure_get_int( pstGstSt1, "height", &nFrameHeight );
	if( !nGboolRes1 ) { g_print( "*** Error: gst_structure_get_int fails to get
snapshot dimension."); return; }

	GstBuffer *pstGstBuffer1;
	pstGstBuffer1 = gst_sample_get_buffer( pstGstSampleInp );
	GstMapInfo stGstMapInfo1;
	gst_buffer_map( pstGstBuffer1, &stGstMapInfo1, GST_MAP_READ );

	cv::Mat oMatTstFrame;
	oMatTstFrame = cv::Mat::zeros( nFrameHeight, nFrameWidth, CV_8UC3 );
	MyfCopyRGBbuf2CvMat( oMatTstFrame, stGstMapInfo1.data );

	gst_buffer_unmap( pstGstBuffer1, &stGstMapInfo1 );

	cv::namedWindow( szgWinTitle, CV_WINDOW_AUTOSIZE );
	cv::imshow( szgWinTitle, oMatTstFrame );
}

//********************************************************************************
int	main( int argc, char *argv[] )
{
	gst_init( &argc, &argv );

	// Describe pipeline
	gchar *szgPipelineDescStr1;
	szgPipelineDescStr1 = g_strdup_printf( "uridecodebin
uri=\"file:///D:/QuickTimeSample.mov\" ! videoconvert ! videoscale ! appsink
name=sink caps=\"video/x-raw,format=RGB\"" ); // Works for both frame and
time seek
	//szgPipelineDescStr1 = g_strdup_printf( "uridecodebin
uri=\"file:///D:/mpts_out.ts\" ! videoconvert ! videoscale ! appsink
name=sink caps=\"video/x-raw,format=RGB\"" ); // NOT works for both frame
and time seek

	// Create pipeline
	GstElement *pstGstElemPipeline1;
	GError *pstGErr1 = NULL;
	pstGstElemPipeline1 = gst_parse_launch( szgPipelineDescStr1, &pstGErr1 );
	if( pstGErr1 != NULL )
	{
		g_print( "could not construct pipeline: %s\n", pstGErr1->message );
		g_error_free( pstGErr1 ); return( -1 );
	}

	// Set to GST_STATE_PAUSED
	GstStateChangeReturn nStateChgRet;
	nStateChgRet = gst_element_set_state( pstGstElemPipeline1, GST_STATE_PAUSED
);
	if( nStateChgRet == GST_STATE_CHANGE_FAILURE ) goto Cleanup;
	nStateChgRet = gst_element_get_state( pstGstElemPipeline1, NULL, NULL, 5 *
GST_SECOND );
	if( nStateChgRet == GST_STATE_CHANGE_FAILURE ) goto Cleanup;

	// Set desired frame number to be displayed
	gint64 nDesiredMediaPosFrameNum = 120;

	// Init required variables
	GstElement *pstGstElemAppSink1;
	pstGstElemAppSink1 = gst_bin_get_by_name( GST_BIN( pstGstElemPipeline1 ),
"sink" );
	gboolean nGboolRes1;
	char *szgWinTitle;

	// Seek by GST_FORMAT_DEFAULT
	nGboolRes1 = gst_element_seek_simple( pstGstElemPipeline1,
GST_FORMAT_DEFAULT,	 (GstSeekFlags) ( GST_SEEK_FLAG_ACCURATE |
GST_SEEK_FLAG_FLUSH ), nDesiredMediaPosFrameNum );
	if( !nGboolRes1 ) { g_print( "*** Error: gst_element_seek_simple by
GST_FORMAT_DEFAULT failed!\n"); }

	// Read sample
	GstSample *pstGstSample1;
	pstGstSample1 = gst_app_sink_pull_preroll( (GstAppSink *)
pstGstElemAppSink1 ); // or g_signal_emit_by_name( pstGstElemAppSink1,
"pull-preroll", &pstGstSample1, NULL );

	// Display sample
	szgWinTitle = g_strdup_printf( "Frame #%lld", nDesiredMediaPosFrameNum );
	MyfDispGstSampleInOpenCvWin( pstGstSample1, szgWinTitle );


	// Set desired position by time to be displayed
	gint64 nDesiredMediaPosNanoSec = 1000 * GST_MSECOND;

	// Seek by GST_FORMAT_DEFAULT
	nGboolRes1 = gst_element_seek_simple( pstGstElemPipeline1, GST_FORMAT_TIME,	
(GstSeekFlags) ( GST_SEEK_FLAG_ACCURATE | GST_SEEK_FLAG_FLUSH ),
nDesiredMediaPosNanoSec );
	if( !nGboolRes1 ) { g_print( "*** Error: gst_element_seek_simple by
GST_FORMAT_TIME failed!\n"); }

	// Read sample
	GstSample *pstGstSample2;
	pstGstSample2 = gst_app_sink_pull_preroll( (GstAppSink *)
pstGstElemAppSink1 );

	// Display sample
	szgWinTitle = g_strdup_printf( "Time %" GST_TIME_FORMAT, GST_TIME_ARGS(
nDesiredMediaPosNanoSec ) );
	MyfDispGstSampleInOpenCvWin( pstGstSample2, szgWinTitle );

Cleanup:
	gst_element_set_state( pstGstElemPipeline1, GST_STATE_NULL );
	gst_object_unref( pstGstElemPipeline1 );

	g_print( "Press any key to finish...\n"); 
	cvWaitKey( 0 );
	return( 0 );
}


Note:
Include directories:
D:\gstreamer\1.0\x86\include\gstreamer-1.0;D:\gstreamer\1.0\x86\include\glib-2.0;D:\gstreamer\1.0\x86\lib\glib-2.0\include;D:\opencv246\build\include\

Library directories:
d:\opencv246\build\x86\vc11\staticlib;D:\gstreamer\1.0\x86\lib




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