L4T Multimedia API Reference27.1 Release |
The video scaling and color format conversion sample demonstrates how to use the libv4l2 video conversion component for image color formatting and buffer layout conversion.
This sample does not require a camera.
Before running the sample, you must have the following:
This sample can be used to convert color format from YV12 to RGB or NV12 to YV12 etc. NVIDIA® Tegra® provides pitch linear and block linear memory format support on input and output. Input and output memory formats do not need to match.
ret = ctx->conv->setOutputPlaneFormat(format.fmt.pix_mp.pixelformat, format.fmt.pix_mp.width, format.fmt.pix_mp.height, NvVideoConverter::LAYOUT_BLOCK);
This call is to set up libv4l2 output plane, i.e., receiving input YUV data for decoder, as a block linear memory format. This is the format that complies with Tegra hardware.
ret = ctx->conv->setCapturePlaneFormat(format.fmt.pix_mp.pixelformat, format.fmt.pix_mp.width, format.fmt.pix_mp.height, NvVideoConverter::LAYOUT_PITCH);
This call sets up libv4l2 capture plane to be pitch linear format. This is the format that is common to software implementation.
v412_videoconvert_test.h
exposes the context_t
global structure to manage all the resources in the application. The key fields in that structure are:
std::queue < \c NvBuffer * > *conv_output_plane_buf_queue
. Holds an output plane queue for the second video converter.The NvVideoDecoder class creates a new V4L2 Video Decoder. The following table describes the key NvVideoDecoder members that this sample uses.
Method | Description |
---|---|
setCapturePlaneFormat | Sets the format on the decoder capture plane. |
setOutputPlaneFormat | Sets the format on the decoder output plane. |
The NvVideoConverter class packages all video converting related elements and functions. It performs color space conversion, scaling and conversion between hardware buffer memory and software buffer memory. The following table describes the key NvVideoConverter members that this sample uses.
Member | Description |
---|---|
output_plane | Holds the output plane. |
capture_plane | Holds the capture plane. |
waitForIdle | Waits until all the buffers queued on the output plane are converted and dequeued from the capture plane. This is a blocking method. |
setCapturePlaneFormat | Sets the format on the converter capture plane. |
setOutputPlaneFormat | Sets the format on the converter output plane. |
NvV4l2ElementPlane creates an NVv4l2Element plane. The following table describes the key NvV4l2ElementPlane members used in this sample.
Member | Description |
---|---|
setupPlane | Sets up the plane of V4l2 element. |
deinitPlane | Destroys the plane of V4l2 element. |
setStreamStatus | Starts/Stops the stream. |
setDQThreadCallback | Sets the callback function of the dqueue buffer thread. |
startDQThread | Starts the thread of the dqueue buffer. |
stopDQThread | Stops the thread of the dqueue buffer. |
qBuffer | Queues a V4l2 buffer from the plane. |
dqBuffer | Dequeues a V4l2 buffer from the plane. |
getNumBuffers | Gets the number of the V4l2 buffer. |
getNumQueuedBuffers | Gets the number of the V4l2 buffer in the queue. |
getNthBuffer | Gets the NvBuffer queue object at index N. |