V4L2 Video Decoder

NVIDIA Tegra V4L2 Video Decoder Description and Extensions. More...


Classes

struct  v4l2_ctrl_videodec_statusmetadata_
 Holds the decoder error status metadata for the frame. More...
struct  v4l2_ctrl_videodec_refframe_metadata_
 Holds the the frame specific metadata for a reference frame. More...
struct  v4l2_ctrl_videodec_currentframe_metadata_
 Holds the the frame specific metadata for the current frame. More...
struct  v4l2_ctrl_videodec_dpbinfometadata_
 Holds the decoder DPB info metadata. More...
struct  v4l2_ctrl_h264dec_bufmetadata_
 Holds H.264 specific decoder metadata for the frame. More...
struct  v4l2_ctrl_hevcdec_bufmetadata_
 Holds H.265 specific decoder metadata for the frame. More...
struct  v4l2_ctrl_videodec_outputbuf_metadata_
 Holds the video decoder output metadata for a frame. More...

Defines

#define V4L2_CID_MPEG_VIDEO_DISABLE_COMPLETE_FRAME_INPUT   (V4L2_CID_MPEG_BASE+515)
 Control ID to indicate to the decoder that the input buffers will not contain complete buffers.
#define V4L2_CID_MPEG_VIDEO_DISABLE_DPB   (V4L2_CID_MPEG_BASE+516)
 Control ID to disable decoder DPB management.
#define V4L2_CID_MPEG_VIDEO_ERROR_REPORTING   (V4L2_CID_MPEG_BASE+517)
 Control ID to enable decoder error and metadata reporting.
#define V4L2_CID_MPEG_VIDEO_SKIP_FRAMES   (V4L2_CID_MPEG_BASE+518)
 Control ID to set the skip frames property of the decoder.
#define V4L2_CID_MPEG_VIDEODEC_METADATA   (V4L2_CID_MPEG_BASE+519)
 Control ID to get the decoder output metadata.

Typedefs

typedef struct
v4l2_ctrl_videodec_statusmetadata_ 
v4l2_ctrl_videodec_statusmetadata
 Holds the decoder error status metadata for the frame.
typedef struct
v4l2_ctrl_videodec_refframe_metadata_ 
v4l2_ctrl_videodec_refframe_metadata
 Holds the the frame specific metadata for a reference frame.
typedef struct
v4l2_ctrl_videodec_currentframe_metadata_ 
v4l2_ctrl_videodec_currentframe_metadata
 Holds the the frame specific metadata for the current frame.
typedef struct
v4l2_ctrl_videodec_dpbinfometadata_ 
v4l2_ctrl_videodec_dpbinfometadata
 Holds the decoder DPB info metadata.
typedef struct
v4l2_ctrl_h264dec_bufmetadata_ 
v4l2_ctrl_h264dec_bufmetadata
 Holds H.264 specific decoder metadata for the frame.
typedef struct
v4l2_ctrl_hevcdec_bufmetadata_ 
v4l2_ctrl_hevcdec_bufmetadata
 Holds H.265 specific decoder metadata for the frame.
typedef struct
v4l2_ctrl_videodec_outputbuf_metadata_ 
v4l2_ctrl_videodec_outputbuf_metadata
 Holds the video decoder output metadata for a frame.

Enumerations

enum  v4l2_skip_frames_type { V4L2_SKIP_FRAMES_TYPE_NONE = 0, V4L2_SKIP_FRAMES_TYPE_NONREF = 1, V4L2_SKIP_FRAMES_TYPE_DECODE_IDR_ONLY = 2 }
 Enum v4l2_skip_frames_type, possible methods for decoder skip frames. More...


Detailed Description

NVIDIA Tegra V4L2 Video Decoder Description and Extensions.

The video decoder device node is "/dev/nvhost-nvdec".

### Supported pixelformats: OUTPUT PLANE | CAPTURE PLANE :----------------: | :----------------: V4L2_PIX_FMT_H264 | V4L2_PIX_FMT_NV12M V4L2_PIX_FMT_H265 | V4L2_PIX_FMT_NV12M

### Supported memory types: MEMORY | OUTPUT PLANE | CAPTURE PLANE :------------------: | :----------: | :-----------: V4L2_MEMORY_MMAP | Y | Y V4L2_MEMORY_DMABUF | N | N V4L2_MEMORY_USERPTR | N | N

### Supported controls:

### Supported events: Event | Purpose ----------------------------- | :----------------------------: V4L2_EVENT_RESOLUTION_CHANGE | Resolution of the stream has changed.

### Handling resolution change events: When the decoder generates a V4L2_EVENT_RESOLUTION_CHANGE event, the application should call STREAMOFF on the capture plane, tell decoder to deallocate the current buffers by calling REQBUF with count zero, get the new capture plane format, and then proceed with setting up the buffers for the capture plane.

In case of decoder, the buffer format might differ from the Display resolution. The application should use VIDIOC_G_CROP to get the display resolution.

### EOS Handling: Following sequence should be followed for sending EOS and recieving EOS from the decoder.

  1. Send EOS to decoder by queueing on the output plane a buffer with bytesused = 0 for the 0th plane (`v4l2_buffer.m.planes[0].bytesused = 0`).
  2. Dequeue buffers on the output plane, till it gets a buffer with bytesused = 0 for the 0th plane (`v4l2_buffer.m.planes[0].bytesused == 0`)
  3. Dequeue buffers on the capture plane, till it gets a buffer with bytesused = 0 for the 0th plane.

### Decoder output frame metadata: Decoder supports reporting frame related metadata including error reports and DPB info. See V4L2_CID_MPEG_VIDEO_ERROR_REPORTING, V4L2_CID_MPEG_VIDEODEC_METADATA and v4l2_ctrl_video_metadata for more information.


Define Documentation

#define V4L2_CID_MPEG_VIDEO_DISABLE_COMPLETE_FRAME_INPUT   (V4L2_CID_MPEG_BASE+515)

Control ID to indicate to the decoder that the input buffers will not contain complete buffers.

Note:
This control should be set in case of frames containing multiple slices when the input buffers do not contain all the slices of the frame.
A boolean value should be supplied with this control.

Attention:
This control should be set before setting formats on either plane.

Definition at line 426 of file v4l2_nv_extensions.h.

#define V4L2_CID_MPEG_VIDEO_DISABLE_DPB   (V4L2_CID_MPEG_BASE+516)

Control ID to disable decoder DPB management.

Note:
This will only work for streams having a single reference frame.
A boolean value should be supplied with this control.

Attention:
This control should be set after setting formats on both the planes and before requesting buffers on either plane.

Definition at line 438 of file v4l2_nv_extensions.h.

#define V4L2_CID_MPEG_VIDEO_ERROR_REPORTING   (V4L2_CID_MPEG_BASE+517)

Control ID to enable decoder error and metadata reporting.

A boolean value should be supplied with this control.

Attention:
This control should be set after setting formats on both the planes and before requesting buffers on either plane.

Definition at line 448 of file v4l2_nv_extensions.h.

#define V4L2_CID_MPEG_VIDEO_SKIP_FRAMES   (V4L2_CID_MPEG_BASE+518)

Control ID to set the skip frames property of the decoder.

Decoder can be configured to skip certain types of frames. One of v4l2_skip_frames_type should be passed.

Attention:
This control should be set after setting formats on both the planes and before requesting buffers on either plane. This control ID is supported only for H264.

Definition at line 460 of file v4l2_nv_extensions.h.

#define V4L2_CID_MPEG_VIDEODEC_METADATA   (V4L2_CID_MPEG_BASE+519)

Control ID to get the decoder output metadata.

Note:
Metadata reporting should be enabled using V4L2_CID_MPEG_VIDEO_ERROR_REPORTING ioctl for this.
A pointer to a valid v4l2_ctrl_video_metadata structure should be supplied with this control.

Attention:
This control should be read after dequeueing a buffer successfully from the capture plane. The values in the structure are valid till the buffer is queued again.

Definition at line 475 of file v4l2_nv_extensions.h.


Typedef Documentation

Holds H.264 specific decoder metadata for the frame.

Holds H.265 specific decoder metadata for the frame.

Holds the the frame specific metadata for the current frame.

Holds the decoder DPB info metadata.

Holds the video decoder output metadata for a frame.

Holds the the frame specific metadata for a reference frame.

Holds the decoder error status metadata for the frame.


Enumeration Type Documentation

Enum v4l2_skip_frames_type, possible methods for decoder skip frames.

Enumerator:
V4L2_SKIP_FRAMES_TYPE_NONE  Do not skip any frame.
V4L2_SKIP_FRAMES_TYPE_NONREF  Skip all non-reference frames.
V4L2_SKIP_FRAMES_TYPE_DECODE_IDR_ONLY  Skip all frames except IDR.

Definition at line 809 of file v4l2_nv_extensions.h.


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