ffmpeg Bmp to yuv : Crash at sws_scale - c++

Question

The context :
I have a succession of continuous bitmap and I want to encode them into a light video format.
I use ffmpeg version 2.8.3 (the build here), under qt5, qt IDE, and msvc2013 for win32.
The problem :
My code crash at sws_scale () (and sometimes at avcodec_encode_video2()). When I explore the stack, the crash event occurs at sws_getCachedContext (). (I can only see the stack with these ffmpeg builds).
I only use these ffmpeg libraries (from the Qt .pro file) :
LIBS += -lavcodec -lavformat -lswscale -lavutil
It's swscale which bug. And this is the code :
void newVideo ()
{
ULONG_PTR gdiplusToken;
GdiplusStartupInput gdiplusStartupInput;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
initBitmap (); //init bmp
int screenWidth = bmp.bmiHeader.biWidth;
int screenHeight = bmp.bmiHeader.biHeight;
AVCodec * codec;
AVCodecContext * c = NULL;
uint8_t * outbuf;
int i, out_size, outbuf_size;
avcodec_register_all();
qDebug () << "Video encoding\n";
// Find the mpeg1 video encoder
codec = avcodec_find_encoder(AV_CODEC_ID_H264);
if (!codec)
{
qDebug () << "Codec not found\n";
avcodec_close(c);
av_free(c);
return;
}
else
qDebug () << "H264 codec found\n";
c = avcodec_alloc_context3(codec);
c->bit_rate = 1000000;
c->width = 800; // resolution must be a multiple of two (1280x720),(1900x1080),(720x480)
c->height = 600;
c->time_base.num = 1; // framerate numerator
c->time_base.den = 25; // framerate denominator
c->gop_size = 30; // emit one intra frame every ten frames
c->max_b_frames = 1; // maximum number of b-frames between non b-frames
c->pix_fmt = AV_PIX_FMT_YUV420P; //Converstion RGB to YUV ?
c->codec_id = AV_CODEC_ID_H264;
struct SwsContext* fooContext = sws_getContext(screenWidth, screenHeight,
AV_PIX_FMT_RGB32,
c->width, c->height,
AV_PIX_FMT_YUV420P,
SWS_FAST_BILINEAR,
NULL, NULL, NULL);
// Open the encoder
if (avcodec_open2(c, codec, NULL) < 0)
{
qDebug () << "Could not open codec\n";
avcodec_close(c);
av_free(c);
return;
}
else qDebug () << "H264 codec opened\n";
outbuf_size = 100000 + c->width*c->height*(32>>3);//*(32>>3); // alloc image and output buffer
outbuf = static_cast<uint8_t *>(malloc(outbuf_size));
qDebug() << "Setting buffer size to: " << outbuf_size << "\n";
FILE* f = fopen("TEST.mpg","wb");
if(!f) qDebug() << "x - Cannot open video file for writing\n";
else qDebug() << "Opened video file for writing\n";
// encode 5 seconds of video
for (i = 0; i < STREAM_FRAME_RATE*STREAM_DURATION; i++) //the stop condition i < 5.0*5
{
qDebug () << "i = " << i;
fflush(stdout);
HBITMAP hBmp;
if (GetScreen(hBmp) == -1) return;
BYTE * pPixels;// = new BYTE [bmp.bmiHeader.biSizeImage];
pPixels = getPixels (hBmp);
DeleteObject (hBmp);
int nbytes = avpicture_get_size(AV_PIX_FMT_YUV420P, c->width, c->height);
uint8_t* outbuffer = (uint8_t*)av_malloc(nbytes*sizeof(uint8_t));
if(!outbuffer) // check if(outbuf) instead
{
qDebug () << "Bytes cannot be allocated";
return;
}
AVFrame* inpic = avcodec_alloc_frame(); //av_frame_alloc () ?
AVFrame* outpic = avcodec_alloc_frame();
outpic->pts = (int64_t)((float)i * (1000.0/((float)(c->time_base.den))) * 90);
if (avpicture_fill((AVPicture*) inpic, (uint8_t*) pPixels, AV_PIX_FMT_RGB32,
screenWidth, screenHeight) < 0)
qDebug () << "avpicture_fill Fill picture with image failed"; //Fill picture with image
if(avpicture_fill((AVPicture*) outpic, outbuffer, AV_PIX_FMT_YUV420P,
c->width, c->height) < 0)
qDebug () << "avpicture_fill failed";
if (av_image_alloc(outpic->data, outpic->linesize, c->width, c->height,
c->pix_fmt, 1) < 0)
qDebug () << "av_image_alloc failed";
inpic->data[0] += inpic->linesize[0]*(screenHeight - 1); // Flipping frame
inpic->linesize[0] = -inpic->linesize[0]; // Flipping frame
////////////////////////////HERE THE BUG////////////////////////////////
sws_scale(fooContext,
inpic->data, inpic->linesize,
0, c->height,
outpic->data, outpic->linesize); //HERE THE BUG
av_free_packet((AVPacket *)outbuf);
// encode the image
out_size = avcodec_encode_video2 (c, (AVPacket *) outbuf,
(AVFrame *) outbuf_size, (int *) outpic);
///////////////////////THE CODE DONT GO BEYOND/////////////////////////////////
qDebug () << "Encoding frame" << i <<" (size=" << out_size <<"\n";
fwrite(outbuf, 1, out_size, f);
delete [] pPixels;
av_free(outbuffer);
av_free(inpic);
av_freep(outpic);
}
// get the delayed frames
for(; out_size; i++)
{
fflush(stdout);
out_size = avcodec_encode_video2 (c, (AVPacket *) outbuf,
(AVFrame *) outbuf_size, NULL);
qDebug () << "Writing frame" << i <<" (size=" << out_size <<"\n";
fwrite(outbuf, 1, out_size, f);
}
// add sequence end code to have a real mpeg file
outbuf[0] = 0x00;
outbuf[1] = 0x00;
outbuf[2] = 0x01;
outbuf[3] = 0xb7;
fwrite(outbuf, 1, 4, f);
fclose(f);
avcodec_close(c);
free(outbuf);
av_free(c);
qDebug () << "Closed codec and Freed\n";
}
And the output :
Video encoding
H264 codec found
H264 codec opened
Setting buffer size to: 2020000
Opened video file for writing
i = 0
**CRASH**
I have thougth that my bitmap wasn't good so I have crafted a bitmap just for testing, the code was :
uint8_t* pPixels = new uint8_t[Width * 3 * Height];
int x = 50;
for(unsigned int i = 0; i < Width * 3 * Height; i = i + 3) // loop for generating color changing images
{
pPixels [i] = x % 255; //R
pPixels [i + 1] = (x) % 255; //G
pPixels [i + 2] = (255 - x) % 255; //B
}
However the crash continue. Perhaps, it might prove that it's not the bitmap (pPixels) which has a problem.
If anyone know, why I get this bug : Maybe don't I set one parameter well ? Or one ffmpeg deprecated function ? etc.
EDIT 1 27/12/15
Thanks to Ronald S. Bultje The function sws_scale () does not crash with this code, however I get an error from it bad dst image pointers. My code:
//DESTINATION FRAME
if (avpicture_alloc ((AVPicture*) dst_frame, AV_PIX_FMT_YUV420P, c->width, c->height) < 0)
{
qDebug () << "# avpicture_alloc failed";
return;
}
if(avpicture_fill((AVPicture*) dst_frame, NULL, AV_PIX_FMT_YUV420P,
c->width, c->height) < 0)
qDebug () << "avpicture_fill failed";
avcodec_align_dimensions2 (c, &c->width, &c->height, dst_frame->linesize);
//SOURCE FRAME
if (avpicture_fill((AVPicture*) src_frame, (uint8_t *) pPixels, AV_PIX_FMT_RGB32,
tmp_screenWidth, tmp_screenHeight) < 0)
qDebug () << "# avpicture_fill Fill picture with image failed"; //Fill picture with image
avcodec_align_dimensions2 (c, &tmp_screenWidth, &tmp_screenHeight, src_frame->linesize);
struct SwsContext* conversionContext = sws_getContext(tmp_screenWidth,tmp_screenHeight,AV_PIX_FMT_RGB32,c->width, c->height, AV_PIX_FMT_YUV420P,SWS_FAST_BILINEAR, NULL, NULL, NULL);
int output_Height = sws_scale(conversionContext,
src_frame->data, src_frame->linesize,
0, tmp_screenHeight,
dst_frame->data, dst_frame->linesize); //return 0 -> bad dst image pointers error
EDIT 2 28/12/15
I have tried to follow the Ronald S. Bultje's suggestion and now I get a bad src image pointers error, I have investigated and worked many hours but I do not find a solution. Here, there is the new snippet :
AVFrame* src_frame = av_frame_alloc ();
AVFrame* dst_frame = av_frame_alloc ();
AVFrame* tmp_src_frame = av_frame_alloc ();
/*........I do not use them until this snippet..........*/
//DESTINATION
//avpicture_free ((AVPicture*)dst_frame);
avcodec_align_dimensions2 (c, &c->width, &c->height, dst_frame->linesize);
if (avpicture_alloc ((AVPicture*) dst_frame, AV_PIX_FMT_YUV420P, c->width, c->height) < 0)
{
qDebug () << "# avpicture_alloc failed";
return;
}
//SOURCE
//stride = src_frame->linesize [0] = ((((screenWidth * bitPerPixel) + 31) & ~31) >> 3); do I need to do that ?
//== stride - I have gotten this formula from : https://msdn.microsoft.com/en-us/library/windows/desktop/dd318229(v=vs.85).aspx
if (avpicture_fill((AVPicture*) src_frame, (uint8_t *) pPixels, AV_PIX_FMT_RGB32,
screenWidth, screenHeight) < 0)
qDebug () << "# avpicture_fill Fill picture with image failed"; //Fill picture with image
//linesize [0] == 21760 like commented stride
//Source TO TMP Source
avcodec_align_dimensions2 (c, &tmp_screenWidth, &tmp_screenHeight, tmp_src_frame->linesize);
if (avpicture_fill((AVPicture*) tmp_src_frame, NULL, AV_PIX_FMT_RGB32,
tmp_screenWidth, tmp_screenHeight) < 0)
qDebug () << "# avpicture_fill Fill picture with image failed"; //Fill picture with image
av_picture_copy ((AVPicture*) tmp_src_frame, (const AVPicture*) src_frame, AV_PIX_FMT_RGB32,
screenWidth, screenHeight);
struct SwsContext* conversionContext = sws_getContext(tmp_screenWidth, tmp_screenHeight,
AV_PIX_FMT_RGB32,
c->width, c->height,
AV_PIX_FMT_YUV420P,
SWS_FAST_BILINEAR,
NULL, NULL, NULL);
int output_Height = sws_scale(conversionContext,
tmp_src_frame->data, tmp_src_frame->linesize,
0, tmp_screenHeight,
dst_frame->data, dst_frame->linesize);
//ffmpeg error = bad src image pointers
// output_Height == 0
EDIT 3
For temp Picture I have done an avcode_align_dimension2() then a avpicture_alloc() for allocating memory and avpicture_fill() in order to fill the picture pointer. Below the updated code:
//DESTINATION
//avpicture_free ((AVPicture*)dst_frame);
avcodec_align_dimensions2 (c, &c->width, &c->height, dst_frame->linesize);
if (avpicture_alloc ((AVPicture*) dst_frame, AV_PIX_FMT_YUV420P, c->width, c->height) < 0)
{
qDebug () << "# avpicture_alloc failed";
return;
}
//SOURCE
//src_frame->linesize [0] = ((((screenWidth * bpp) + 31) & ~31) >> 3);
//src_frame->linesize [0] = stride;
if (avpicture_fill((AVPicture*) src_frame, (uint8_t *) pPixels, AV_PIX_FMT_RGB32,
screenWidth, screenHeight) < 0)
qDebug () << "# avpicture_fill Fill picture with image failed"; //Fill picture with image
//Source TO TMP Source
avcodec_align_dimensions2 (c, &tmp_screenWidth, &tmp_screenHeight, tmp_src_frame->linesize);
if (avpicture_alloc ((AVPicture*) tmp_src_frame, AV_PIX_FMT_RGB32, tmp_screenWidth, tmp_screenHeight) < 0)
{
qDebug () << "# avpicture_alloc failed";
return;
}
int outbuf_size = tmp_screenWidth*tmp_screenHeight*4;// alloc image and output buffer
outbuf = static_cast<uint8_t *>(malloc(outbuf_size));
if (avpicture_fill((AVPicture*) tmp_src_frame, outbuf, AV_PIX_FMT_RGB32,
tmp_screenWidth, tmp_screenHeight) < 0)
qDebug () << "# avpicture_fill Fill picture with image failed"; //Fill picture with image
av_picture_copy ((AVPicture*) tmp_src_frame, (const AVPicture*) src_frame, AV_PIX_FMT_RGB32,
tmp_screenWidth, tmp_screenHeight);
struct SwsContext* conversionContext = sws_getContext(tmp_screenWidth, tmp_screenHeight,
AV_PIX_FMT_RGB32,
c->width, c->height,
AV_PIX_FMT_YUV420P,
SWS_FAST_BILINEAR,
NULL, NULL, NULL);
int output_Height = sws_scale(conversionContext,
tmp_src_frame->data, tmp_src_frame->linesize,
0, tmp_screenHeight,
dst_frame->data, dst_frame->linesize);
The call stack is as follow : av_picture_copy() is called then av_image_copy() then _VEC_memcpy() then fastcopy_I() and crash ... The problem is not the dimensions (tmp_screenWidth/Height) ? (With av_picture_copy () could we copy a picture P1 with dim W1xH1 to a picture P2 with dimension W2xH2 ?)
EDIT 4
Crash at av_picture_copy() which call _aligned_malloc() then av_image_copy _VEC_memcpy() and fastcopy_I()
//SOURCE
if (avpicture_fill((AVPicture*) src_frame, (uint8_t *) pPixels, AV_PIX_FMT_RGB32,
screenWidth, screenHeight) < 0)
qDebug () << "# avpicture_fill Fill picture with image failed"; //Fill picture with image
//Source TO TMP Source
avcodec_align_dimensions2 (c, &tmp_screenWidth, &tmp_screenHeight, tmp_src_frame->linesize);
if (avpicture_alloc ((AVPicture*) tmp_src_frame, AV_PIX_FMT_RGB32, tmp_screenWidth, tmp_screenHeight) < 0)
{
qDebug () << "# avpicture_alloc failed";
return;
}
av_picture_copy ((AVPicture*) tmp_src_frame, (const AVPicture*) src_frame, AV_PIX_FMT_RGB32,
tmp_screenWidth, tmp_screenHeight);

Answer 1

You're using avpicture_fill(), which is implemented like this:
int avpicture_fill(AVPicture *picture, const uint8_t *ptr,
enum AVPixelFormat pix_fmt, int width, int height)
{
return av_image_fill_arrays(picture->data, picture->linesize,
ptr, pix_fmt, width, height, 1);
}
Note the last argument to av_image_fill_arrays(), align=1. This means buffer lines will be unaligned. Unfortunately, and this isn't clear at all in the documentation, most FFmpeg functions require buffer lines to be aligned to a power-of-two that allows SSE2 or AVX2 optimizations, e.g. align=32. See the second bullet point in this response on how to do that programmatically.
Aside, in your test code, you're using new (instead of av_malloc) to allocate memory, and the returned pointer from new is also not guaranteed to be aligned by 32 byte.