Access violation reading location 0x000000148965F000 - c++

Question

I tried to encode BMP Images, which i get from a buffer and store it as a H264 Video. I am stuck with these errors the arrive randomly and repeatedly
I am using Visual Studio 2012
1) Access violation reading location 0x000000148965F000.
2)Heap corruption
The debug shows the error at this point
struct SwsContext* fooContext = sws_getContext(_imgWidth,_imgHeight,PIX_FMT_RGB32,c->width,c->height,PIX_FMT_YUV420P, SWS_FAST_BILINEAR,NULL,NULL,NULL);
sws_scale(fooContext, inpic->data, inpic->linesize, 0, c->height, outpic->data, outpic->linesize); // converting frame size and format
I guess the read violation happens due to non - pre initialized values. But i couldnt exactly understand why. I have also attached part of the code below
PagedImage *inImg = getUpdatedInputImage(0);
ML_CHECK(inImg);
ImageVector imgExt = inImg->getImageExtent();
if ((imgExt.x == _imgWidth) && (imgExt.y == _imgHeight))
{
if (((imgExt.x % 4) == 0) && ((imgExt.y % 4) == 0))
{
_numFramesFld->setIntValue(_numFramesFld->getIntValue() + 1);
MLFree(unicodeFilename);
// configure header
//BITMAPINFO bitmapInfo
// read out input image and write output image into video
// get input image as an array
void* imgData = NULL;
SubImageBox imageBox(imgExt); // get the whole image
getTile(inImg, imageBox, MLuint8Type, &imgData);
MLuint8* iData = (MLuint8*)imgData;
// since we have only images with
// a z-ext of 1, we can compute the c stride as follows
int cStride = _imgWidth * _imgHeight;
int offset = 0;
MLuint8 r=0, g=0, b=0;
// pointer into the bitmap that is
// used to write images into an video
UCHAR* dst = (UCHAR*)_bits;
for (int y = _imgHeight-1; y >= 0; y--)
{ // reversely scan the image. if y-rows of DIB are set in normal order, no compression will be available.
offset = _imgWidth * y;
for (int x = 0; x < _imgWidth; x++)
{
if (_isGreyValueImage)
{
r = iData[offset + x];
*dst++ = (UCHAR)r;
*dst++ = (UCHAR)r;
*dst++ = (UCHAR)r;
}
else
{
b = iData[offset + x]; // windows bitmap need reverse order: bgr instead of rgb
g = iData[offset + x + cStride ];
r = iData[offset + x + cStride + cStride];
*dst++ = (UCHAR)r;
*dst++ = (UCHAR)g;
*dst++ = (UCHAR)b;
}
// alpha channel in input image is ignored
}
}
outbuf_size = 100000 + c->width*c->height*(32>>3); // allocate output buffer
outbuf = static_cast<uint8_t *>(malloc(outbuf_size));
fileName_ = (_outputFilenameFld->getStringValue()).c_str();
FILE* f = fopen(fileName_,"wb"); // opening video file for writing
if(!f)
{
_messageFld->setStringValue("Cannot open file");
}
else _messageFld->setStringValue("Opened video file for writing\n");
//for(i=0;i<_numFramesFld->getIntValue();i++)
//{
fflush(stdout);
int nbytes = avpicture_get_size(PIX_FMT_YUV420P, c->width, c->height); // allocating outbuffer
uint8_t* outbuffer = (uint8_t*)av_malloc(nbytes*sizeof(uint8_t));
AVFrame* inpic = avcodec_alloc_frame(); // mandatory frame allocation
AVFrame* outpic = avcodec_alloc_frame();
//outpic->pts = (int64_t)((float)i * (1000.0/((float)(c->time_base.den))) * 90); // setting frame pts
avpicture_fill((AVPicture*)inpic,(uint8_t*)dst, PIX_FMT_RGB32, c->width, c->height); // fill image with input screenshot
avpicture_fill((AVPicture*)outpic, outbuffer, PIX_FMT_YUV420P, c->width, c->height); // clear output picture for buffer copy
av_image_alloc(outpic->data, outpic->linesize, c->width, c->height, c->pix_fmt, 1);
inpic->data[0] += inpic->linesize[0]*(c->height-1); // flipping frame
inpic->linesize[0] = -inpic->linesize[0]; // flipping frame
struct SwsContext* fooContext = sws_getContext(_imgWidth,_imgHeight,PIX_FMT_RGB32,c->width,c->height,PIX_FMT_YUV420P, SWS_FAST_BILINEAR,NULL,NULL,NULL);
sws_scale(fooContext, inpic->data, inpic->linesize, 0, c->height, outpic->data, outpic->linesize); // converting frame size and format
out_size = avcodec_encode_video(c, outbuf, outbuf_size, outpic); // encoding video
_messageFld->setStringValue("Encoding frame %3d (size=%5d)\n");
fwrite(outbuf, 1, out_size, f);
delete [] dst; // freeing memory
av_free(outbuffer);
av_free(inpic);
av_free(outpic);
av_free(fooContext);
DeleteObject(_hbitmap);
for(int Z = 0; Z<out_size; i++)
{
fflush(stdout);
out_size = avcodec_encode_video(c, outbuf, outbuf_size, outpic); // encode the delayed frames
fwrite(outbuf, 1, out_size, f);
}
//outbuf[0] = 0x00;
//outbuf[1] = 0x00; // add sequence end code to have a real mpeg file
//outbuf[2] = 0x01;
//outbuf[3] = 0xb7;
//fwrite(outbuf, 1, 4, f);
fclose(f);
avcodec_close(c); // freeing memory
free(outbuf);
av_free(c);
printf("Closed codec and Freed\n");
}
}

Answer 1

Access violation could be tricky to debug.
Since you have a Read Access Violation, it could be that somewhere you have run over your pointers with data and only now, when you try to read from there, you get the exception.
I recommend you use GFLAGS with Full PageHeap to pinpoint exactly the location of your AccessViolation:
gflags /p /enable ImageFileName /full.
GFlags and PageHeap
I hope this will help