rebuild_scaler_from_frame()

bool MayaFlux::IO::VideoStreamContext::rebuild_scaler_from_frame	(	const AVFrame *	frame,
		uint32_t	target_width = 0,
		uint32_t	target_height = 0,
		int	target_format = -1
	)

Rebuild the SwsContext using the pixel format resolved from a live decoded frame.

dshow and similar capture devices on Windows leave pix_fmt as AV_PIX_FMT_NONE until the first decoded frame arrives. Call this once from the camera's frame-receive loop on the very first valid AVFrame to finalise the scaler before calling sws_scale.

Parameters

frame	The first successfully decoded AVFrame.
target_width	Desired output width (0 = keep frame width).
target_height	Desired output height (0 = keep frame height).
target_format	Desired AVPixelFormat (negative = AV_PIX_FMT_RGBA).

Returns

True if the scaler was (re)initialised successfully.

Definition at line 352 of file VideoStreamContext.cpp.

{
    if (!frame || frame->width <= 0 || frame->height <= 0
        || frame->format == AV_PIX_FMT_NONE) {
        m_last_error = "rebuild_scaler_from_frame: invalid frame";
        return false;
    }
 
    if (codec_context && codec_context->pix_fmt == AV_PIX_FMT_NONE)
        codec_context->pix_fmt = static_cast<AVPixelFormat>(frame->format);
 
    if (width == 0 || height == 0) {
        width = static_cast<uint32_t>(frame->width);
        height = static_cast<uint32_t>(frame->height);
    }
    src_pixel_format = codec_context ? codec_context->pix_fmt : frame->format;
 
    if (sws_context) {
        sws_freeContext(sws_context);
        sws_context = nullptr;
    }
 
    const uint32_t use_w = tw > 0 ? tw : (target_width > 0 ? target_width : width);
    const uint32_t use_h = th > 0 ? th : (target_height > 0 ? target_height : height);
    const int use_f = tf >= 0 ? tf : (target_format >= 0 ? target_format : -1);
 
    return setup_scaler(use_w, use_h, use_f);
}

References codec_context, height, m_last_error, setup_scaler(), src_pixel_format, sws_context, target_format, target_height, target_width, and width.

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