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CANN V100R020C10 Application Software Development Guide (Python) 01
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VDEC

VDEC

Functions and Restrictions

Functions and Restrictions

The video decoder (VDEC) decodes videos. After VPC processing, the VDEC outputs YUV420SP images (including NV12 and NV21).

  • Input description

    • Input resolution range:

      128 x 128 to 4096 x 4096

    • Input formats:

      H.264 BP/MP/HP Level 5.1 YUV420SP encoded streams

      H.265 8-bit/10-bit Level 5.1 YUV420 encoded streams

    • Input memory:

      Allocate memory by calling acl.rt.malloc and free memory by calling acl.rt.free. Alternatively, allocate memory by calling acl.media.dvpp_malloc and free memory by calling acl.media.dvpp_free.

  • Output description

    • Output image formats:

      • YUV420SP NV12

      • YUV420SP NV21

    • Output memory:

      • Calculate the output memory size according to the image format.

        YUV420SP: widthStride x heightStride x 3/2

      • The start address of the output memory must be 16-byte aligned. Allocate memory by calling acl.media.dvpp_malloc and free memory by calling acl.media.dvpp_free.

    • widthStride and heightStride alignment:

      • widthStride: Round up the input width to the nearest multiple of 16.

      • heightStride: Round up the input height to the nearest multiple of 2.

  • The VDEC decodes input streams frame by frame.

  • Bad frames or frame loss in the streams may cause VDEC frame loss.

  • The VDEC cannot decode the streams encoded in interlaced scanning mode.

Performance Specifications

  • The recommended number of channels (n) for VDEC decoding is as follows:

    720p indicates a resolution of 1280 x 720 pixels. 1080p indicates a resolution of 1920 x 1080 pixels. 4K indicates a resolution of 3840 x 2160 pixels.

    Resolution

    Total Frame Rate

    Single-channel performance (n)

    Memory Consumption Per VDEC Channel (for Reference Only)

    3840*2160

    120fps

    120 fps/n (n = 4 is recommended, 30 fps per channel.)

    About 170 MB

    1920*1080

    480fps

    480 fps/n (n = 16 is recommended, 30 fps per channel.)

    About 86 MB

    ≤1280*720

    960fps

    960 fps/n (n = 32 is recommended, 30 fps per channel.)

    About 70 MB

  • Suggestions on the number of decoding channels and frame rate:

    The specifications in the following table are for reference only. If the number of channels started in a single process exceeds the specifications in the following table, memory insufficiency or performance drop may occur, leading to decoding channel creation failures and slow decoding.

    720p indicates a resolution of 1280 x 720 pixels. 1080p indicates a resolution of 1920 x 1080 pixels. 4K indicates a resolution of 3840 x 2160 pixels.

    Typical Resolution

    Suggested Channel Count Per Process (Based on the Input Frame Rate)

    -

    Input frame rate ≥ 25 fps

    20 fps < input frame rate < 25 fps

    15 fps < input frame rate ≤ 20 fps

    10 fps < input frame rate ≤ 15 fps

    Input frame rate ≤ 10 fps

    ≤720p

    32 channels

    32 channels

    32 channels

    32 channels

    32 channels

    1080p

    16 channels

    19 channels

    24 channels

    32 channels

    32 channels

    4K

    4 channels

    4 channels

    6 channels

    8 channels

    12 channels

Function: vdec_create_frame_config

C Prototype

aclvdecFrameConfig *aclvdecCreateFrameConfig()

Python Function

vdec_frame_config = acl.media.vdec_create_frame_config()

Function Usage

Creates data of the aclvdecFrameConfig type as the single-frame encoding configuration. It is a synchronous interface.

Input Description

None

Return Value

vdec_frame_config: int, pointer to data of the aclvdecFrameConfig type object.

  • If a non-zero value is returned, the operation is successful.
  • If 0 is returned, the operation fails.

Restrictions

None

Precautions

None

Function: vdec_destroy_frame_config

C Prototype

aclError aclvdecDestroyFrameConfig(aclvdecFrameConfig *vdecFrameConfig)

Python Function

ret = acl.media.vdec_destroy_frame_config(vdec_frame_config)

Function Usage

Destroys the configuration data created by calling acl.media.vdec_create_frame_config. It is a synchronous interface.

Input Description

vdec_frame_config: int, data to be destroyed.

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

Destruction API: The released or destroyed resources are no longer available after this API is called. You are advised to set the released or destroyed resources to invalid values (for example, 0 or None) after calling this API.

Precautions

None

Function: vdec_create_channel

C Prototype

aclError aclvdecCreateChannel(aclvdecChannelDesc *channelDesc)

Python Function

ret = acl.media.vdec_create_channel(vdec_channel_desc)

Function Usage

Creates a channel for video data processing. A channel can be reused. After being destroyed, the channel is no longer available. It is a synchronous interface.

acl.rt.create_stream is encapsulated in the acl.media.vdec_create_channel to explicitly create a stream. acl.rt.subscribe_report specifies the thread for processing the callback function on the stream. The callback function and thread are specified when users call acl.media.vdec_set_channel_desc series.

When implementing the VDEC function, you do not need to call acl.rt.create_stream and acl.rt.subscribe_report separately.

Input Description

vdec_channel_desc: int, VDEC channel description address object, description of the specified channel.

acl.media.vdec_create_channel_desc is called to create data of the vdec_channel_desc type, and acl.media.vdec_set_channel_desc series is called to set the attributes of the channel description.

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

None

Precautions

None

Function: vdec_destroy_channel

C Prototype

aclError aclvdecDestroyChannel(aclvdecChannelDesc *channelDesc)

Python Function

ret = acl.media.vdec_destroy_channel(vdec_channel_desc)

Function Usage
  • Destroys a channel created by calling acl.media.vdec_create_channel for video data processing. It is a synchronous interface.
  • The channel is destroyed after the transmitted frames are decoded and the callback function is handled.
  • acl.media.vdec_destroy_channel encapsulates the acl.rt.unsubscribe_report to unsubscribe a thread (callback function in the stream is no longer processed by the specified thread), and acl.rt.destroy_stream destroys a stream.
  • When implementing the VDEC function, you do not need to call acl.rt.unsubscribe_report and acl.rt.destroy_stream separately.

Input Description

vdec_channel_desc: int, VDEC channel description address object, description of the specified channel. It must be the same as the vdec_channel_desc argument passed to the acl.media.vdec_create_channel call.

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

Destruction API: The released or destroyed resources are no longer available after this API is called. You are advised to set the released or destroyed resources to invalid values (for example, 0 or None) after calling this API.

Precautions

None

Function: vdec_create_channel_desc

C Prototype

aclvdecChannelDesc *aclvdecCreateChannelDesc()

Python Function

vdec_channel_desc = acl.media.vdec_create_channel_desc()

Function Usage

Creates data of the vdec_channel_desc type to describe a video decoding channel. It is a synchronous interface.

Input Description

None

Return Value

vdec_channel_desc: int, VDEC channel description address object.

  • If data of the vdec_channel_desc type is returned, the operation is successful.
  • If 0 is returned, the operation fails.

Restrictions

None

Precautions

None

Function: vdec_destroy_channel_desc

C Prototype

aclError aclvdecDestroyChannelDesc(aclvdecChannelDesc *channelDesc)

Python Function

ret = acl.media.vdec_destroy_channel_desc(vdec_channel_desc)

Function Usage

Destroys the vdec_channel_desc data. Only the vdec_channel_desc data created by calling acl.media.vdec_create_channel_desc can be destroyed. It is a synchronous interface.

Input Description

vdec_channel_desc: int, VDEC channel description address object, data to be destroyed.

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

Destruction API: The released or destroyed resources are no longer available after this API is called. You are advised to set the released or destroyed resources to invalid values (for example, 0 or None) after calling this API.

Precautions

None

Function: vdec_set_channel_desc_channel_id

C Prototype

aclError aclvdecSetChannelDescChannelId(aclvdecChannelDesc *channelDesc, uint32_t channelId)

Python Function

ret = acl.media.vdec_set_channel_desc_channel_id(vdec_channel_desc, channel_id)

Function Usage

Sets the decoding channel description attribute: decoding channel ID.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

channel_id: int, decoding channel ID. The value range is [0, 31].

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

None

Precautions

None

Function: vdec_set_channel_desc_thread_id

C Prototype

aclError aclvdecSetChannelDescThreadId(aclvdecChannelDesc *channelDesc, uint64_t threadId)

Python Function

ret = acl.media.vdec_set_channel_desc_thread_id(vdec_channel_desc, thread_id)

Function Usage

Sets the decoding channel description attribute: callback thread ID.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

thread_id: int, callback thread ID.

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

It is not allowed to pass the same thread ID for registering different VDEC callback functions on different devices in the same process.

Precautions

None

Function: vdec_set_channel_desc_callback

C Prototype

aclError aclvdecSetChannelDescCallback(aclvdecChannelDesc *channelDesc, aclvdecCallback callback)

Python Function

ret = acl.media.vdec_set_channel_desc_callback(vdec_channel_desc, callback)

Function Usage

Sets the decoding channel description attribute: callback function.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

callback: Python function object, callback function.

  • Callback function format in Python:

    def vdec_call_back_func(dvpp_stream_desc, dvpp_pic_desc, user_data):

    pass

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

None

Precautions

None

Function: vdec_set_channel_desc_entype

C Prototype

aclError aclvdecSetChannelDescEnType(aclvdecChannelDesc *channelDesc, acldvppStreamFormat enType)

Python Function

ret = acl.media.vdec_set_channel_desc_entype(vdec_channel_desc, entype)

Function Usage

Sets the decoding channel description attribute: video encoding protocol.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

entype: int, video encoding protocol.

  • 0: H265_MAIN_LEVEL
  • 1: H264_BASELINE_LEVEL
  • 2: H264_MAIN_LEVEL
  • 3: H264_HIGH_LEVEL

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

None

Precautions

None

Function: vdec_set_channel_desc_out_pic_format

C Prototype

aclError aclvdecSetChannelDescOutPicFormat(aclvdecChannelDesc *channelDesc, acldvppPixelFormat outPicFormat)

Python Function

ret = acl.media.vdec_set_channel_desc_out_pic_format(vdec_channel_desc, out_pic_format)

Function Usage

Sets the decoding channel description attribute: YUV image storage format.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

out_pic_format: int, YUV image storage format.

  • For details, see dvpp_set_pic_desc_format.

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

None

Precautions

If acl.vdec.set_channel_desc_out_pic_format is not called to set the output format, images in YUV420SP NV12 are output by default.

Function: vdec_set_channel_desc_out_pic_width

C Prototype

aclError aclvdecSetChannelDescOutPicWidth(aclvdecChannelDesc *channelDesc, uint32_t outPicWidth)

Python Function

ret = acl.media.vdec_set_channel_desc_out_pic_width(vdec_channel_desc, out_pic_width)

Function Usage

Sets the decoding channel description attribute: image width.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

out_pic_width: int, maximum output width.

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

None

Precautions

None

Function: vdec_set_channel_desc_out_pic_height

C Prototype

aclError aclvdecSetChannelDescOutPicHeight(aclvdecChannelDesc *channelDesc, uint32_t outPicHeight)

Python Function

ret = acl.media.vdec_set_channel_desc_out_pic_height(vdec_channel_desc, out_pic_height)

Function Usage

Sets the decoding channel description attribute: image height.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

out_pic_height: int, maximum output height.

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

None

Precautions

None

Function: vdec_set_channel_desc_ref_frame_num

C Prototype

aclError aclvdecSetChannelDescRefFrameNum(aclvdecChannelDesc *channelDesc, uint32_t refFrameNum)

Python Function

ret = acl.media.vdec_set_channel_desc_ref_frame_num(vdec_channel_desc, ref_frame_num)

Function Usage

Sets the decoding channel description attribute: number of reference frames.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

ref_frame_num: int, number of reference frames. The value range is [0, 16].

Return Value

ret: int, error code.

  • 0 indicates success.
  • Other values indicate failure.

Restrictions

None

Precautions

None

Function: vdec_get_channel_desc_channel_id

C Prototype

uint32_t aclvdecGetChannelDescChannelId(const aclvdecChannelDesc *channelDesc)

Python Function

channel_id = acl.media.vdec_get_channel_desc_channel_id(vdec_channel_desc)

Function Usage

Obtains the decoding channel description attribute: decoding channel ID.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

Return Value

channel_id: int, decoding channel ID. The value range is [0, 31].

Restrictions

None

Precautions

None

Function: vdec_get_channel_desc_thread_id

C Prototype

uint32_t aclvdecGetChannelDescThreadId(const aclvdecChannelDesc *channelDesc);

Python Function

thread_id = acl.media.vdec_get_channel_desc_thread_id(vdec_channel_desc)

Function Usage

Obtains the decoding channel description attribute: callback thread ID.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

Return Value

thread_id: int, callback thread ID.

Restrictions

None

Precautions

None

Function: vdec_get_channel_desc_callback

C Prototype

aclvdecCallback aclvdecGetChannelDescCallback(const aclvdecChannelDesc *channelDesc)

Python Function

callback = acl.media.vdec_get_channel_desc_callback(vdec_channel_desc)

Function Usage

Obtains the decoding channel description attribute: callback function.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

Return Value

callback: Python function object, callback function.

  • Callback function format in Python:

    def vdec_call_back_func(dvpp_stream_desc, dvpp_pic_desc, user_data):

    pass

Restrictions

None

Precautions

None

Function: vdec_get_channel_desc_entype

C Prototype

acldvppStreamFormat aclvdecGetChannelDescEnType(const aclvdecChannelDesc *channelDesc);

Python Function

entype = acl.media.vdec_get_channel_desc_entype(vdec_channel_desc)

Function Usage

Obtains the decoding channel description attribute: video encoding protocol.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

Return Value

entype: int, video encoding protocol.

H265_MAIN_LEVEL = 0

H264_BASELINE_LEVEL = 1

H264_MAIN_LEVEL = 2

H264_HIGH_LEVEL = 3

Restrictions

None

Precautions

None

Function: vdec_get_channel_desc_out_pic_format

C Prototype

acldvppPixelFormat aclvdecGetChannelDescOutPicFormat(const aclvdecChannelDesc *channelDesc);

Python Function

out_pic_format = acl.media.vdec_get_channel_desc_out_pic_format(vdec_channel_desc)

Function Usage

Obtains the decoding channel description attribute: YUV image storage format.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

Return Value

out_pic_format: int, YUV image storage format. For details, see dvpp_set_pic_desc_format.

Restrictions

None

Precautions

None

Function: vdec_get_channel_desc_out_pic_width

C Prototype

uint32_t aclvdecGetChannelDescOutPicWidth(const aclvdecChannelDesc *channelDesc);

Python Function

out_pic_width = acl.media.vdec_get_channel_desc_out_pic_width(vdec_channel_desc)

Function Usage

Obtains the decoding channel description attribute: image width.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

Return Value

out_pic_width: int, image width.

Restrictions

None

Precautions

None

Function: vdec_get_channel_desc_out_pic_height

C Prototype

uint32_t aclvdecGetChannelDescOutPicHeight(const aclvdecChannelDesc *channelDesc);

Python Function

out_pic_height = acl.media.vdec_get_channel_desc_out_pic_height(vdec_channel_desc)

Function Usage

Obtains the decoding channel description attribute: image height.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

Return Value

out_pic_height: int, image height.

Restrictions

None

Precautions

None

Function: vdec_get_channel_desc_ref_frame_num

C Prototype

uint32_t aclvdecGetChannelDescRefFrameNum(const aclvdecChannelDesc *channelDesc)

Python Function

ref_frame_num = acl.media.vdec_get_channel_desc_ref_frame_num(vdec_channel_desc)

Function Usage

Obtains the decoding channel description attribute: number of reference frames.

Input Description

vdec_channel_desc: int, VDEC channel description address object, to describe a video decoding channel.

Return Value

ref_frame_num: int, number of reference frames. The value range is [0, 16].

Restrictions

None

Precautions

None
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Updated: 2021-02-23

Document ID: EDOC1100164845

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