SMEM: Bad dst image pointers when using format_callback - c++

Question

I'm trying to get frames from video stream and use them as OpenCV Mat, but I have encountered a problem.
I don't know the resolution my video stream will have so I use
libvlc_video_set_format_callbacks
but then, after video starts playing, I hear audio, but I'm not getting an image, instead I get errors:
Bad dst image pointers.
Here's my code:
struct ctx
{
unsigned char *pixeldata;
std::mutex imagemutex;
};
static void *lock(void *data, void **p_pixels)
{
struct ctx *ctx = reinterpret_cast<struct ctx *>(data);
ctx->imagemutex.lock();
*p_pixels = ctx->pixeldata;
return NULL;
}
static void unlock(void *data, void *id, void *const *p_pixels)
{
struct ctx *ctx = reinterpret_cast<struct ctx *>(data);
ctx->imagemutex.unlock();
assert(id == NULL);
}
unsigned setup(void **opaque, char *chroma, unsigned *width, unsigned *height, unsigned *pitches, unsigned *lines)
{
struct ctx *callback = reinterpret_cast<struct ctx *>(*opaque);
unsigned nWidth = (*width);
unsigned nHeight = (*height);
(*pitches) = nWidth * 3;
(*lines) = nHeight;
chroma = (char *)"RV24";
callback->pixeldata = new unsigned char[nWidth*nHeight*3];
return 1;
}
int main(int argc, char *argv[])
{
libvlc_instance_t *vlcInstance;
libvlc_media_player_t *_player;
libvlc_media_t *_media;
const char * const vlc_args[] = {
"-I", "dummy", // Don't use any interface
"--ignore-config", // Don't use VLC's config
"--extraintf=logger", // Log anything
"--verbose=2", // Be much more verbose then normal for debugging purpose
};
vlcInstance = libvlc_new(sizeof(vlc_args) / sizeof(vlc_args[0]), vlc_args);
_media = libvlc_media_new_location(vlcInstance , "rtsp://address");
_player = libvlc_media_player_new_from_media(_media);
struct ctx *callback = new struct ctx;
libvlc_video_set_callbacks(_player, lock, unlock, 0, callback);
libvlc_video_set_format_callbacks(_player, setup, 0);
libvlc_media_player_play(_player);
}
If I won't use libvlc_video_set_format_callbacks(_player, setup, 0); but instead set fixed parameters, eg. libvlc_video_set_format(_player, "RV24", 720, 404, 720 * 3); it works fine. Any idea what might be a problem?

Answer 1

Actually it was simple and stupid mistake.
Line:
chroma = (char *)"RV24";
needs to be replaced by:
memcpy(chroma, "RV24", 4);