The VideoLAN Forums

Posted: **29 Oct 2015 15:17**

Here is my format callback using the VMEM output module.

static unsigned int format_callback(
	void **data,
	char *chroma,
	unsigned *width,
	unsigned *height,
	unsigned *pitches,
	unsigned *lines)
{
	HRESULT hr = S_OK;
	CMediaPlayer::Context* context = (CMediaPlayer::Context*)(*data);

	video_format_t format;
	ZeroMemory(&format, sizeof(video_format_t));

	vlc_mutex_init(&context->mutex);
	video_format_Setup(&format, vlc_fourcc_GetCodecFromString(VIDEO_ES, chroma), *width, *height, *width, *height, 0, 0);

	format.i_chroma = vlc_fourcc_GetCodecFromString(VIDEO_ES, chroma);
	picture_t* picture = picture_NewFromFormat(&format);

	context->picture = picture;

	for (int planeNumber = 0; planeNumber < picture->i_planes; planeNumber++)
	{
		pitches[planeNumber] = picture->p[planeNumber].i_pitch;
		lines[planeNumber] = picture->p[planeNumber].i_lines;
	}

	context->planesSwapped = false;
	if (picture->format.i_chroma == VLC_CODEC_I420 ||
		picture->format.i_chroma == VLC_CODEC_J420 ||
		picture->format.i_chroma == VLC_CODEC_YV12) {
		/* The dx/d3d buffer is always allocated as YV12 */
		if (vlc_fourcc_AreUVPlanesSwapped(picture->format.i_chroma, VLC_CODEC_YV12)) {
			context->planesSwapped = true;
		}
	}

	context->window1 = WindowContext::Create(context->parent1, format.i_visible_width, format.i_visible_height);
	context->window2 = WindowContext::Create(context->parent2, format.i_visible_width, format.i_visible_height);

	return context->picture->i_planes;
}

Windows Media Player shows the dimensions of the video as 720x480. It is 2 pixels less (width) than what format_callback is telling me.

Here is what the image looks like when I am rendering.

My renderer has been rendering videos fine. It is just this video. I think it is related to the fact that the dimensions are reported different in VLC, than in Windows Media Player. Can someone help guide my on this issue?

Posted: **29 Oct 2015 15:40**

Ok, so I am playing around with things, having no clue what I am doing, and I added 16 pixels of width to the renderer I build, and it works.

Code: Select all

	context->window1 = WindowContext::Create(context->parent1, format.i_visible_width + 16, format.i_visible_height);
	context->window2 = WindowContext::Create(context->parent2, format.i_visible_width + 16, format.i_visible_height);

However, this now breaks the normal videos that never gave me an issue.

What am I missing here? I'm not getting it.

Posted: **29 Oct 2015 17:20**

Ok, so using the pitch created from picture_NewFromFormat resolved both cases.

Code: Select all

	context->window1 = WindowContext::Create(context->parent1, pitches[0], format.i_visible_height);
	context->window2 = WindowContext::Create(context->parent2, pitches[0], format.i_visible_height);

However, now my 720x480 has a lot of empty pixels on the side of the video. So, I made a little check to determine if the generated pitch is larger than my with, otherwise, regenerate a new image with 16 pixels less. This method is not ideal because I am allocating more images than I intend to use. Here is my updated solution that works for both videos, and doesn't add a gutter of empty pixels.

Code: Select all

static unsigned int format_callback(
	void **data,
	char *chroma,
	unsigned *width,
	unsigned *height,
	unsigned *pitches,
	unsigned *lines)
{
	picture_t* picture = NULL;

	HRESULT hr = S_OK;
	CMediaPlayer::Context* context = (CMediaPlayer::Context*)(*data);

	video_format_t format;
	ZeroMemory(&format, sizeof(video_format_t));

	vlc_mutex_init(&context->mutex);
	video_format_Setup(&format, vlc_fourcc_GetCodecFromString(VIDEO_ES, chroma), *width, *height, *width, *height, 0, 0);
	format.i_chroma = vlc_fourcc_GetCodecFromString(VIDEO_ES, chroma);
	picture = picture_NewFromFormat(&format);
	context->picture = picture;

	if (picture->p[0].i_pitch > *width)
	{
		// delete old picture so we can allocate new one with 16 pixels less width
		picture_Release(picture);
		picture = NULL;
		context->picture = NULL;

		*width = *width - 16;

		video_format_Setup(&format, vlc_fourcc_GetCodecFromString(VIDEO_ES, chroma), *width, *height, *width, *height, 0, 0);
		format.i_chroma = vlc_fourcc_GetCodecFromString(VIDEO_ES, chroma);
		picture = picture_NewFromFormat(&format);
		context->picture = picture;
	}

	for (int planeNumber = 0; planeNumber < picture->i_planes; planeNumber++)
	{
		LOG(INFO) << "pitch:" << picture->p[planeNumber].i_pitch;
		LOG(INFO) << "lines:" << picture->p[planeNumber].i_lines;
		pitches[planeNumber] = picture->p[planeNumber].i_pitch;
		lines[planeNumber] = picture->p[planeNumber].i_lines;
	}

	assert(0 == pitches[0] % 4 && 0 == pitches[1] % 4 && 0 == pitches[2] % 4);

	context->planesSwapped = false;
	if (picture->format.i_chroma == VLC_CODEC_I420 ||
		picture->format.i_chroma == VLC_CODEC_J420 ||
		picture->format.i_chroma == VLC_CODEC_YV12) {
		/* The dx/d3d buffer is always allocated as YV12 */
		if (vlc_fourcc_AreUVPlanesSwapped(picture->format.i_chroma, VLC_CODEC_YV12)) {
			context->planesSwapped = true;
		}
	}

	context->window1 = WindowContext::Create(context->parent1, pitches[0], format.i_visible_height);
	context->window2 = WindowContext::Create(context->parent2, pitches[0], format.i_visible_height);

	return context->picture->i_planes;
}

I'm blindly fixing this. I really need to know what is going on. But hey, it's working!

Posted: **29 Oct 2015 17:29**

You should really not mix the plugin and external API in the same code. If you depend on the plugin API anyway, you might as well write a plugin, and the issue should be moot.

The VideoLAN Forums

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Playing back a 720x482 video using VMEM, distorting image.

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Re: Playing back a 720x482 video using VMEM, distorting image.

Re: Playing back a 720x482 video using VMEM, distorting image.