# qtivcomposer The qtivcomposer plugin uses the GPU hardware to merge/mix several input video streams into a single output stream. Note In a live source setup using a qtivcomposer, long-duration testing indicated that if input buffers don’t arrive at the expected intervals, the composer may produce duplicate output frames. When this duplication persists across consecutive frames, it can create a visual impression that the video has frozen, even though the buffers are continuously generated and processed. This behavior suggests that the irregular buffer timing can disrupt normal frame generation which result in misleading playback artifacts. The pad properties determine the composition of the input buffers (for each stream) in the output buffer. - The following table lists a few common pad properties of qtivcomposer. For more information, see [Table : Pad properties of qtivcomposer](https://docs.qualcomm.com/doc/80-80021-50/topic/qtivcomposer.html#section-edf-jcn-myb). - . | Property | Usage | | --- | --- | | Position | Sets the X and Y axes placement of each input frame within the output. | | Crop | Sets the optional crop for the source. | | Dimensions | Upscales/downscales the frames. | | Rotate | Rotates the frames at right angles | |


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> | Flips the frames horizontally and vertically. | | Alpha | Adds the alpha blending value to the frames. | | Z order | Changes the order of the frames.


By default, the frames are organized in the order in which the sink pads are created. For example, sink\_0, and sink\_1. | The figure shows the GStreamer pipeline using qtivcomposer that’s working with several video sources. GST BIN GstBuffer + GstMemory: Image + GstVideoMeta: Describes the raw video data GstBuffer + GstMemory: Image + GstVideoMeta: Describes the raw video data video/x-rawwidth=1920, height=1080, format=YUV video/x-rawwidth=1920 height=1080format=YUV video/x-rawwidth=640, height=360, format=BGRA video/x-rawwidth=1280, height=720, format=RGB video/x-rawwidth=320, height=180, format=YUV2 qtivcomposer filesink Video source 0 Video source 1 Video source N-1 Video source N-2 Qualcomm Open source **Figure : Pipeline with qtivcomposer** The video compositions include, but aren’t limited to the following: - Picture-in-picture - Side-by-side - Alpha blending If no composition parameters and dimensions are specified in the [GstCaps](https://gstreamer.freedesktop.org/documentation/gstreamer/gstcaps.html) source pad, the output video frames will have the same dimensions as the biggest incoming video stream. Similarly, if the frame rate isn’t set in GstCaps, it’s taken from the stream with the highest frame rate. And if output GstCaps doesn’t have an explicitly set format, the plugin negotiates the most common format based on the input streams. The plugin uses the Qualcomm IB2C library or Qualcomm Computer Vision SDK for all the transformation operations. - The Qualcomm IB2C library is wrapped in the custom GstC2dVideoConverter or GstGlesVideoConverter abstraction layer. - It contains APIs to create, configure, and process the incoming and outgoing buffers. - The recommended plugin is GstGLESVideoConverter. A custom buffer pool class called GstImageBufferPool allocates the output buffers. GstImageBufferPool allocates either GBM or ION buffers: - The GBM allocation is done through the Qualcomm libgbm. - The ION allocation is done through IOCTL commands to the kernel. ## Inheritance chain [GObject](https://docs.gtk.org/gobject/) → [GstObject](https://gstreamer.freedesktop.org/documentation/gstreamer/gstobject.html?gi-language=c) → [GstElement](https://gstreamer.freedesktop.org/documentation/gstreamer/gstelement.html?gi-language=c) → [GstAggregator](https://gstreamer.freedesktop.org/documentation/base/gstaggregator.html?gi-language=c) → GstVideoComposer The following tables provide information on pad templates and element properties of qtivcomposer. For use cases, see [Video composition use cases](https://docs.qualcomm.com/doc/80-80021-50/topic/video-composition.html). ## Pad configuration | Pad Name | Capabilities | Capabilities | Capabilities | | --- | --- | --- | --- | |
SINK template: 'sink\_%u'



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> | video/x-raw | format: | { (string)NV12, (string)NV21, (string)UYVY, (string)YUY2, (string)RGBA, (string)BGRA, (string)ARGB, (string)ABGR, (string)RGBx, (string)BGRx, (string)xRGB, (string)xBGR, (string)RGB, (string)BGR, (string)GRAY8 } | |
SINK template: 'sink\_%u'



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> | video/x-raw | width: | [ 1, 32767 ] | |
SINK template: 'sink\_%u'



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> | video/x-raw | height: | [ 1, 32767 ] | |
SINK template: 'sink\_%u'



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> | video/x-raw | framerate: | [ 0/1, 255/1 ] | |
SINK template: 'sink\_%u'



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> | video/x-raw(memory:GBM) | format: | { (string)NV12, (string)NV21, (string)UYVY, (string)YUY2, (string)RGBA, (string)BGRA, (string)ARGB, (string)ABGR, (string)RGBx, (string)BGRx, (string)xRGB, (string)xBGR, (string)RGB, (string)BGR, (string)GRAY8 } | |
SINK template: 'sink\_%u'



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> | video/x-raw(memory:GBM) | width: | [ 1, 32767 ] | |
SINK template: 'sink\_%u'



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> | video/x-raw(memory:GBM) | height: | [ 1, 32767 ] | |
SINK template: 'sink\_%u'



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> | video/x-raw(memory:GBM) | framerate: | [ 0/1, 255/1 ] | |
SRC template: 'src'



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> | video/x-raw | format: | { (string)NV12, (string)NV21, (string)UYVY, (string)YUY2, (string)RGBA, (string)BGRA, (string)ARGB, (string)ABGR, (string)RGBx, (string)BGRx, (string)xRGB, (string)xBGR, (string)RGB, (string)BGR, (string)GRAY8 } | |
SRC template: 'src'



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> | video/x-raw | width: | [ 1, 32767 ] | |
SRC template: 'src'



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> | video/x-raw | height: | [ 1, 32767 ] | |
SRC template: 'src'



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> | video/x-raw | framerate: | [ 0/1, 255/1 ] | |
SRC template: 'src'



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> | video/x-raw(memory:GBM) | format: | { (string)NV12, (string)NV21, (string)UYVY, (string)YUY2, (string)RGBA, (string)BGRA, (string)ARGB, (string)ABGR, (string)RGBx, (string)BGRx, (string)xRGB, (string)xBGR, (string)RGB, (string)BGR, (string)GRAY8 } | |
SRC template: 'src'



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> | video/x-raw(memory:GBM) | width: | [ 1, 32767 ] | |
SRC template: 'src'



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> | video/x-raw(memory:GBM) | height: | [ 1, 32767 ] | |
SRC template: 'src'



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> | video/x-raw(memory:GBM) | framerate: | [ 0/1, 255/1 ] | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pad | Property | Description | | --- | --- | --- | | 'sink\_%u' | zorder | - Z axis order, the default is the order of creation.
- | | 'sink\_%u' | crop | - The crop rectangle ('<X, Y, WIDTH, HEIGHT>').
- | | 'sink\_%u' | position | - The X and Y coordinates of the destination rectangle upper left corner ('<X, Y>').
- | | 'sink\_%u' | dimensions | - The destination rectangle width and height, if left as '0' they're the same as input dimensions ('<WIDTH, HEIGHT>')
- | | 'sink\_%u' | alpha | - Alpha channel value.
- | | 'sink\_%u' | flip-horizontal | - Flip the video image horizontally.
- | | 'sink\_%u' | flip-vertical | - Flip the video image vertically.
- | | 'sink\_%u' | rotate | - Rotate the video image.
- | | 'sink\_%u' | emit-signals | - Send signals to signal data consumption.
- | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | ## Element configuration Table : Element properties of qtivcomposer | Property | Description | | --- | --- | | name | - The name of the object.
- | | parent | - The parent of the object.
- | | engine | - Engine backend used for the conversion operations.
- | | latency | - Additional latency in live mode allows upstream to take longer to produce buffers for the current position (in nanoseconds).
- | | start-time-selection | - Decides which start time is output.
- | | start-time | - Start time to use if start-time-selection=set.
- | | background | - Background color.
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