[Live-devel] MJPEG woes

[Andy Bell]

Hi,

I have been trying to use Live555 to stream a JPEG file to OpenRTSP and
other Live555 based clients.

Depending on the source JPEG file I get varying results in quality.  When
streaming the JPEG file I am simply finding the SOS marker and copying this
to fTo, the code is below.  I am starting to think that I need to be
something else here as at the client side, for example OpenRTSP, isn't the
exact same image.

For example, if I connect to an IP camera, streaming MJPEG, with OpenRTSP I
can get an image saved as a JPEG using:

./openRTSP -m rtsp://....

I then use this same image with the code below and use openRTSP again to
stream the image and I get something far blockier.

Where am I going wrong?

Thanks in advance
Andy

TestJPEGVideoSource* TestJPEGVideoSource::createNew(UsageEnvironment& env,
const char * fileName, unsigned int timePerFrame)

{

FILE * fid = fopen( fileName, "r" );

 if ( fid == NULL )

{

env.setResultErrMsg( "Failed to open input device file" );

return NULL;

}

 return new TestJPEGVideoSource( env, fid, timePerFrame );

}


TestJPEGVideoSource::TestJPEGVideoSource(UsageEnvironment& env, FILE* fid,
unsigned int timePerFrame)

: JPEGVideoSource(env), fFid(fid), fTimePerFrame(timePerFrame),
fNeedAFrame(False)

{

this->buffer = NULL;

fseek( fid, 0L, SEEK_END );

size_t sz = ftell( fFid );

fseek( fid, 0L, SEEK_SET );

 buffer = new unsigned char[ sz ];

fread( buffer, 1, sz, fid );

bool sof0 = false;

bool sos = false;

this->sosIndex = 0;

this->sosSize = 0;

 for ( int i = 0; i < (int)(sz - 8); ++i )

{

if ( buffer[i] == 0xFF && buffer[i+1] == 0xC0)

{

fLastHeight = (buffer[i+5]<<5)|(buffer[i+6]>>3);

fLastWidth = (buffer[i+7]<<5)|(buffer[i+8]>>3);

if ( sos && sof0 ) break;

}

else if ( buffer[i] == 0xFF && buffer[i+1] == 0xDA )

{

sosIndex = i + 2;

if ( sos && sof0 ) break;

}

 }

 if ( this->sosIndex > 0 )

this->sosSize = sz - this->sosIndex;

 printf( "Streaming image w=%d h=%d total_size=%d sos_size=%d\n", fLastWidth
* 8, fLastHeight * 8, (int)sz, this->sosSize );

fclose(fFid);

}


TestJPEGVideoSource::~TestJPEGVideoSource()

{

if ( this->buffer ) delete [] buffer;

}


void TestJPEGVideoSource::doGetNextFrame()

{

fFrameSize = this->sosSize;

 if ( fFrameSize > fMaxSize )

{

printf( "Truncating frame!!\n" );

fNumTruncatedBytes = fFrameSize - fMaxSize;

fFrameSize = fMaxSize;

}

 memcpy( fTo, this->buffer + this->sosIndex, fFrameSize );

 if ( fPresentationTime.tv_sec == 0 && fPresentationTime.tv_usec == 0 )

{

gettimeofday( &fPresentationTime, NULL );

}

else

{

unsigned uSeconds = fPresentationTime.tv_usec + ( fTimePerFrame * 1000 );

fPresentationTime.tv_sec += uSeconds / 1000000;

fPresentationTime.tv_usec = uSeconds % 1000000;

}


fDurationInMicroseconds = fTimePerFrame * 1000;

 nextTask() = envir().taskScheduler().scheduleDelayedTask( 0,
(TaskFunc*)FramedSource::afterGetting, this );

}

u_int8_t TestJPEGVideoSource::type()

{

return 1;

}

u_int8_t TestJPEGVideoSource::qFactor()

{

return 65;

}

u_int8_t TestJPEGVideoSource::width()

{

return fLastWidth;

}

u_int8_t TestJPEGVideoSource::height()

{

return fLastHeight;

}
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