venc_create_chn

Applicability

Product	Supported
Atlas 350 Accelerator Card	√
Atlas A3 training product / Atlas A3 inference product	√
Atlas A2 training product / Atlas A2 inference product	√
Atlas training product	x
Atlas inference product	√
Atlas 200I/500 A2 inference product	√

Description

Creates an encoding channel.

Prototype

C Prototype

        
             hi_s32 hi_mpi_venc_create_chn(hi_venc_chn chn, const hi_venc_chn_attr *attr)

Python Function

        
             ret = acl.himpi.venc_create_chn(chn, attr)

Parameters

Parameter	Description
chn	Int, decoding channel ID. NOTE: For Ascend virtual instances on the Atlas inference product , total number of VENC and JPEGE channels = (Total number of allocated VENC and JPEGE hardware units/Total number of VENC and JPEGE hardware units) x 256. If the total number of channels is not an integer, round down the value. For Ascend virtual instances on the Atlas A2 training product / Atlas A2 inference product , the maximum number of JPEGE channels is 256. For Ascend virtual instances on the Atlas 200I/500 A2 inference product , the number of VENC channels is calculated as follows: Number of VENC channels = (Allocated VENC hardware units/Total VENC hardware units) x 128. If the total number of channels is not an integer, round down the value. The number of JPEGE channels is not affected by the computing power. However, the maximum number of JPEGE+VENC channels is 128. To view the computing power specifications of Ascend virtual instances in different scenarios, run the npu-smi info -t template-info command on the server where AI processor is installed.
attr	Dict, dictionary of encoding channel attributes. For details, see hi_venc_chn_attr.

Parameter

Description

chn

Int, decoding channel ID.

NOTE:

For Ascend virtual instances on the Atlas inference product , total number of VENC and JPEGE channels = (Total number of allocated VENC and JPEGE hardware units/Total number of VENC and JPEGE hardware units) x 256. If the total number of channels is not an integer, round down the value.

For Ascend virtual instances on the Atlas A2 training product / Atlas A2 inference product , the maximum number of JPEGE channels is 256.

For Ascend virtual instances on the Atlas 200I/500 A2 inference product , the number of VENC channels is calculated as follows: Number of VENC channels = (Allocated VENC hardware units/Total VENC hardware units) x 128. If the total number of channels is not an integer, round down the value. The number of JPEGE channels is not affected by the computing power. However, the maximum number of JPEGE+VENC channels is 128.

To view the computing power specifications of Ascend virtual instances in different scenarios, run the npu-smi info -t template-info command on the server where AI processor is installed.

attr

Dict, dictionary of encoding channel attributes. For details, see hi_venc_chn_attr.

Return Value

Return Value	Description
ret	Int, error code. 0 indicates success. Other values indicate failure. For details, see VENC/JPEGE Return Codes.

Restrictions

The channel ID of a single device must not be greater than the maximum channel ID.
An encoding channel has the encoder attributes, RC attributes, and group of pictures (GOP) attributes.
For the encoder attributes, you must set the parameters such as the encoding stream buffer depth, stream obtaining mode, and encoding profile. The Table 1 describes the features of each attribute of each protocol.
The recommended encoding sizes are 3840 x 2160 (4K), 1920 x 1080 (1080p), and 1280 x 720 (720p).
For H.264/H.265 encoding, a frame buffer consists of YHeaderSize, CHeaderSize, YSize, CSize, PmeSize, PmeInfoSize, and TmvSize. The encoder calculates the buffer allocation based on the maximum width and height by default. When configuring the channel width and height, ensure that each frame buffer calculated based on the channel width and height is within that calculated based on the maximum channel width and height.
The input/output frame rate (src_frame_rate/dst_frame_rate) in the attributes of the bit rate controller is used to allocate the bit rate (bit_rate) during encoding, but not the final display frame rate of the player. For details about how to set the display frame rate, see acl.himpi.venc_set_h264_vui or acl.himpi.venc_set_h265_vui.
You are advised to set the control frame rate to be the same as the display frame rate. Otherwise, the bit rate during playback may be different from the encoding bit rate configured by the user, and the playback bit rate will vary with the configured display frame rate.

Reference

For details about the API call sequence, see JPEGE and VENC.

References

**Table 1** Restrictions on encoder attributes
Encode Protocol	Encode Mode	Stream Buffer Depth	Stream Fetching Mode	Encode Profile
H.264	Frame	When mini_buf_mode = 0: Buffer allocation ≥ max_pic_width x max_pic_height x 3/4 When mini_buf_mode = 1: Buffer allocation ≥ 32 x 1024 bytes	Frame/Slice	Baseline Main Profile High Profile
JPEG	Frame	If mini_buf_mode is set to 0 and the original image format is YUV420, the minimum buffer size is calculated as follows: Minimum buffer size = 16-aligned original image width x 16-aligned original image height x 3/2. If the original image format is YUV422 packed, the minimum buffer size is calculated as follows: Minimum buffer size = 16-aligned width of the original image x 16-aligned height of the original image x 2 When mini_buf_mode = 1: Buffer allocation ≥ 32 x 1024 bytes	Frame/Ecs	Baseline
H.265	Frame	When mini_buf_mode = 0: Buffer allocation ≥ max_pic_width x max_pic_height x 3/4 When mini_buf_mode = 1: Buffer allocation ≥ 32 x 1024 bytes	Frame/Slice	Main Profile Main 10 Profile (not supported currently)
H.265	Frame	When mini_buf_mode = 0, Buffer ≥ max_pic_width * max_pic_height * (3/4) * (5/4). When mini_buf_mode = 1: Buffer allocation ≥ 32 x 1024 bytes	Frame/Slice	Main 10 profile (not supported currently)

Parent topic: VENC/JPEGE APIs