Failing to properly initialize AVFrame for sws_scale conversion - opengl

Question

I'm decoding video using FFMpeg, and want to edit the decoded frames using OpenGL, but in order to do that I need to convert the data in AVFrame from YUV to RGB.
In order to do that I create a new AVFrame:
AVFrame *inputFrame = av_frame_alloc();
AVFrame *outputFrame = av_frame_alloc();
av_image_alloc(outputFrame->data, outputFrame->linesize, width, height, AV_PIX_FMT_RGB24, 1);
av_image_fill_arrays(outputFrame->data, outputFrame->linesize, NULL, AV_PIX_FMT_RGB24, width, height, 1);
Create a conversion context:
struct SwsContext *img_convert_ctx = sws_getContext(width, height, AV_PIX_FMT_YUV420P,
width, height, AV_PIX_FMT_RGB24,
0, NULL, NULL, NULL);
And then try to convert it to RGB:
sws_scale(img_convert_ctx, (const uint8_t *const *)&inputFrame->data, inputFrame->linesize, 0, inputFrame->height, outputFrame->data, outputFrame->linesize);
But this causes an "[swscaler # 0x123f15000] bad dst image pointers" error during run time. When I went over FFMpeg's source I found out that the reason is that outputFrame's data wasn't initialized, but I don't understand how it should be.
All existing answers or tutorials that I found (see example) seem to use deprecated APIs, and it's unclear how to use the new APIs. I'd appreciate any help.

Answer 1

Here's how I call sws_scale:
image buf2((buf.w + 15)/16*16, buf.h, 3);
sws_scale(sws_ctx, (const uint8_t * const *)frame->data, frame->linesize, 0, c->height, (uint8_t * const *)buf2.c, &buf2.ys);
There are two differences here:
You pass &inputFrame->data but it shall be inputFrame->data without the address-of operator.
You don't have to allocate a second frame structure. The sws_scale doesn't care about it. It just needs a chunk of memory of the proper size (and maybe alignment).

Answer 2

In my case the av_image_alloc / av_image_fill_arrays did not create the frame->data pointers.
Here is how I did it, not sure if everything is correct, but it works:
d->m_FrameCopy = av_frame_alloc();
uint8_t* buffer = NULL;
int numBytes;
// Determine required buffer size and allocate buffer
numBytes = avpicture_get_size(
AV_PIX_FMT_RGB24, d->m_Frame->width, d->m_Frame->height);
buffer = (uint8_t*)av_malloc(numBytes * sizeof(uint8_t));
avpicture_fill(
(AVPicture*)d->m_FrameCopy,
buffer,
AV_PIX_FMT_RGB24,
d->m_Frame->width,
d->m_Frame->height);
d->m_FrameCopy->format = AV_PIX_FMT_RGB24;
d->m_FrameCopy->width = d->m_Frame->width;
d->m_FrameCopy->height = d->m_Frame->height;
d->m_FrameCopy->channels = d->m_Frame->channels;
d->m_FrameCopy->channel_layout = d->m_Frame->channel_layout;
d->m_FrameCopy->nb_samples = d->m_Frame->nb_samples;