`VENC` Module API Manual#

Overview#

This manual provides a detailed introduction to the API of the K230_CanMV VENC module. Developers can use these APIs to perform video encoding, generating streams of different resolutions and encoding formats. The VENC module needs to be used in conjunction with the camera module to achieve encoding functionality.

API Introduction#

The VENC module provides the Encoder class, which includes the following methods:

Encoder.init#

Description

Constructor to initialize the encoder instance.

Syntax

encoder = Encoder()

Parameters

Parameter Name	Description	Input/Output
None

Return Value

Return Value	Description
Encoder Object	Encoder Object

`Encoder.SetOutBufs`#

Description

Configures the output buffer of the encoder.

Syntax

Encoder.SetOutBufs(chn, buf_num, width, height)

Parameters

Parameter Name	Description	Input/Output
chn	Encoding channel number	Input
buf_num	Number of output buffers	Input
width	Width of the encoded image	Input
height	Height of the encoded image	Input

Return Value

Return Value	Description
None

Notes

Must be called before MediaManager.init()

`Encoder.Create`#

Description

Creates an encoder instance.

Syntax

Encoder.Create(chn, chnAttr)

Parameters

Parameter Name	Description	Input/Output
chn	Encoding channel number	Input
chnAttr	Encoding channel attribute structure	Input

Return Value

Return Value	Description
None

Notes

VENC supports up to 4 encoding channels, with channel numbers ranging from [0, 3]. The 4th channel is fixed for IDE image transmission. Unless calling compress_for_ide, it is recommended to use only [0, 2].

`Encoder.Start`#

Description

Starts the encoding process.

Syntax

Encoder.Start(chn)

Parameters

Parameter Name	Description	Input/Output
chn	Encoding channel number	Input

Return Value

Return Value	Description
None

`Encoder.SendFrame`#

Description

Sends image data to the encoder for encoding.

Syntax

Encoder.SendFrame(venc_chn, frame_info)

Parameters

Parameter Name	Description	Input/Output
chn	Encoding channel number	Input
frame_info	Raw image information structure	Input

Return Value

Return Value	Description
0	Success
Non-zero	Failure

Notes

Can encode a full frame of data or a variable-length data stream.

`Encoder.GetStream`#

Description

Gets a frame of encoded stream data.

Syntax

Encoder.GetStream(chn, streamData,timeout=-1)

Parameters

Parameter Name	Description	Input/Output
chn	Encoding channel number	Input
streamData	Encoded stream structure	Output
timeout	Obtain the bitstream timeout. Value range: [-1, +∞ ) -1：Blocking. 0: Non-blocking.Greater than 0: Timeout period.	Input

Return Value

Return Value	Description
0	Success
Non-zero	Failure

`Encoder.ReleaseStream`#

Description

Releases a frame of stream buffer.

Syntax

Encoder.ReleaseStream(chn, streamData)

Parameters

Parameter Name	Description	Input/Output
chn	Encoding channel number	Input
streamData	Encoded stream structure	Input

Return Value

Return Value	Description
None

`Encoder.Stop`#

Description

Stops the encoding process.

Syntax

Encoder.Stop(chn)

Parameters

Parameter Name	Description	Input/Output
chn	Encoding channel number	Input

Return Value

Return Value	Description
None

`Encoder.Destroy`#

Description

Destroys the encoder instance.

Syntax

Encoder.Destroy(chn)

Parameters

Parameter Name	Description	Input/Output
chn	Encoding channel number	Input

Return Value

Return Value	Description
None

Data Structure Description#

`ChnAttrStr`#

Description

Encoding channel attribute structure.

Definition

class ChnAttrStr:
    def __init__(self, payloadType, profile, picWidth, picHeight,bit_rate = 4000,gopLen = 30,src_frame_rate = 30,dst_frame_rate = 30,mjpeg_quality_factor = 45):
        self.payload_type = payloadType
        self.profile = profile
        self.pic_width = picWidth
        self.pic_height = picHeight
        self.gop_len = gopLen
        self.bit_rate = bit_rate
        self.src_frame_rate = src_frame_rate
        self.dst_frame_rate = dst_frame_rate
        self.mjpeg_quality_factor = mjpeg_quality_factor

Members

Member Name	Description
payload_type	Encoding format (h264/h265)
profile	Encoding Profile
pic_width	Image width
pic_height	Image height
gop_len	Encoding GOP length
bit_rate	Bitrate
src_frame_rate	Input frame rate
dst_frame_rate	Output frame rate
mjpeg_quality_factor	MJPEG encoding quality factor (image quality compression ratio parameter)

`StreamData`#

Description

Stream structure.

Definition

class StreamData:
    def __init__(self):
        self.data = [0 for i in range(0, VENC_PACK_CNT_MAX)]
        self.phy_addr = [0 for i in range(0, VENC_PACK_CNT_MAX)]
        self.data_size = [0 for i in range(0, VENC_PACK_CNT_MAX)]
        self.stream_type = [0 for i in range(0, VENC_PACK_CNT_MAX)]
        self.pts = [0 for i in range(0, VENC_PACK_CNT_MAX)]
        self.pack_cnt = 0

Members

Member Name	Description
data	Stream data address
phy_addr	Physical address of the code stream
data_size	Stream data size
stream_type	Frame type
pts	Display the timestamp
pack_cnt	Number of packs in the stream

Notes

VENC_PACK_CNT_MAX indicates the maximum number of packs in the stream structure, currently set to 12.

`payload_type`#

Description

Encoding format type.

Members

Member Name	Description
PAYLOAD_TYPE_H264	H.264 encoding format
PAYLOAD_TYPE_H265	H.265 encoding format

`profile`#

Description

Encoding Profile.

Members

Member Name	Description
H264_PROFILE_BASELINE	H.264 Baseline Profile
H264_PROFILE_MAIN	H.264 Main Profile
H264_PROFILE_HIGH	H.264 High Profile
H265_PROFILE_MAIN	H.265 Main Profile

`stream_type`#

Description

Stream frame type.

Members

Member Name	Description
STREAM_TYPE_HEADER	Stream Header
STREAM_TYPE_I	I Frame
STREAM_TYPE_P	P Frame

Example Programs#

Example 1#

Bind VENC to VICAP and save the obtained encoded data to a file.

from media.vencoder import *
from media.sensor import *
from media.media import *
import time, os

def vi_bind_venc_test(file_name, width=1280, height=720):
    print("VENC test starts")
    venc_chn = VENC_CHN_ID_0
    width = ALIGN_UP(width, 16)
    venc_payload_type = K_PT_H264

    # Determine file extension
    suffix = file_name.split('.')[-1]
    if suffix == '264':
        venc_payload_type = K_PT_H264
    elif suffix == '265':
        venc_payload_type = K_PT_H265
    else:
        print("Unknown file extension")
        return

    # Initialize sensor
    sensor = Sensor()
    sensor.reset()
    sensor.set_framesize(width=width, height=height, alignment=12)
    sensor.set_pixformat(Sensor.YUV420SP)

    # Instantiate video encoder
    encoder = Encoder()
    encoder.SetOutBufs(venc_chn, 8, width, height)

    # Bind camera and venc
    link = MediaManager.link(sensor.bind_info()['src'], (VIDEO_ENCODE_MOD_ID, VENC_DEV_ID, venc_chn))

    # Initialize media manager
    MediaManager.init()

    if (venc_payload_type == K_PT_H264):
        chnAttr = ChnAttrStr(encoder.PAYLOAD_TYPE_H264, encoder.H264_PROFILE_MAIN, width, height)
    elif (venc_payload_type == K_PT_H265):
        chnAttr = ChnAttrStr(encoder.PAYLOAD_TYPE_H265, encoder.H265_PROFILE_MAIN, width, height)

    streamData = StreamData()

    # Create encoder
    encoder.Create(venc_chn, chnAttr)

    # Start encoding
    encoder.Start(venc_chn)
    # Start camera
    sensor.run()

    frame_count = 0
    print("Save stream to file: ", file_name)

    with open(file_name, "wb") as fo:
        try:
            while True:
                os.exitpoint()
                encoder.GetStream(venc_chn, streamData)  # Get a frame of stream

                for pack_idx in range(0, streamData.pack_cnt):
                    stream_data = uctypes.bytearray_at(streamData.data[pack_idx], streamData.data_size[pack_idx])
                    fo.write(stream_data)  # Write stream to file
                    print("Stream size: ", streamData.data_size[pack_idx], "Stream type: ", streamData.stream_type[pack_idx])

                encoder.ReleaseStream(venc_chn, streamData)  # Release a frame of stream

                frame_count += 1
                if frame_count >= 200:
                    break
        except KeyboardInterrupt as e:
            print("User stop: ", e)
        except BaseException as e:
            import sys
            sys.print_exception(e)

    # Stop camera
    sensor.stop()
    # Destroy the binding of camera and venc
    del link
    # Stop encoding
    encoder.Stop(venc_chn)
    # Destroy encoder
    encoder.Destroy(venc_chn)
    # Clean buffer
    MediaManager.deinit()
    print("VENC test stops")

if __name__ == "__main__":
    os.exitpoint(os.EXITPOINT_ENABLE)
    vi_bind_venc_test("/sdcard/examples/test.264", 800, 480)  # Example of binding vi to venc

Example 2#

Encode VENC data stream and save it as a file. Here’s the translated text to English:

from media.vencoder import *
from media.sensor import *
from media.media import *
import time, os

def stream_venc_test(file_name, width=1280, height=720):
    print("venc_test start")
    venc_chn = VENC_CHN_ID_0
    width = ALIGN_UP(width, 16)
    venc_payload_type = K_PT_H264

    # Determine file type
    suffix = file_name.split('.')[-1]
    if suffix == '264':
        venc_payload_type = K_PT_H264
    elif suffix == '265':
        venc_payload_type = K_PT_H265
    else:
        print("Unknown file extension")
        return

    # Initialize sensor
    sensor = Sensor()
    sensor.reset()
    # Set camera output buffer
    # Set chn0 output size
    sensor.set_framesize(width=width, height=height, alignment=12)
    # Set chn0 output format
    sensor.set_pixformat(Sensor.YUV420SP)

    # Instantiate video encoder
    encoder = Encoder()
    # Set video encoder output buffer
    encoder.SetOutBufs(venc_chn, 8, width, height)

    # Initialize media manager
    MediaManager.init()

    if (venc_payload_type == K_PT_H264):
        chnAttr = ChnAttrStr(encoder.PAYLOAD_TYPE_H264, encoder.H264_PROFILE_MAIN, width, height)
    elif (venc_payload_type == K_PT_H265):
        chnAttr = ChnAttrStr(encoder.PAYLOAD_TYPE_H265, encoder.H265_PROFILE_MAIN, width, height)

    streamData = StreamData()

    # Create encoder
    encoder.Create(venc_chn, chnAttr)

    # Start encoding
    encoder.Start(venc_chn)
    # Start camera
    sensor.run()

    frame_count = 0
    print("save stream to file: ", file_name)

    yuv420sp_img = None
    frame_info = k_video_frame_info()
    with open(file_name, "wb") as fo:
        try:
            while True:
                os.exitpoint()
                yuv420sp_img = sensor.snapshot(chn=CAM_CHN_ID_0)
                if (yuv420sp_img == -1):
                    continue

                frame_info.v_frame.width = yuv420sp_img.width()
                frame_info.v_frame.height = yuv420sp_img.height()
                frame_info.v_frame.pixel_format = Sensor.YUV420SP
                frame_info.pool_id = yuv420sp_img.poolid()
                frame_info.v_frame.phys_addr[0] = yuv420sp_img.phyaddr()
                # frame_info.v_frame.phys_addr[1] = yuv420sp_img.phyaddr(1)
                if (yuv420sp_img.width() == 800 and yuv420sp_img.height() == 480):
                    frame_info.v_frame.phys_addr[1] = frame_info.v_frame.phys_addr[0] + frame_info.v_frame.width * frame_info.v_frame.height + 1024
                elif (yuv420sp_img.width() == 1920 and yuv420sp_img.height() == 1080):
                    frame_info.v_frame.phys_addr[1] = frame_info.v_frame.phys_addr[0] + frame_info.v_frame.width * frame_info.v_frame.height + 3072
                elif (yuv420sp_img.width() == 640 and yuv420sp_img.height() == 360):
                    frame_info.v_frame.phys_addr[1] = frame_info.v_frame.phys_addr[0] + frame_info.v_frame.width * frame_info.v_frame.height + 3072
                else:
                    frame_info.v_frame.phys_addr[1] = frame_info.v_frame.phys_addr[0] + frame_info.v_frame.width * frame_info.v_frame.height

                encoder.SendFrame(venc_chn, frame_info)
                encoder.GetStream(venc_chn, streamData)  # Get a frame of stream

                for pack_idx in range(0, streamData.pack_cnt):
                    stream_data = uctypes.bytearray_at(streamData.data[pack_idx], streamData.data_size[pack_idx])
                    fo.write(stream_data)  # Write stream to file
                    print("stream size: ", streamData.data_size[pack_idx], "stream type: ", streamData.stream_type[pack_idx])

                encoder.ReleaseStream(venc_chn, streamData)  # Release a frame of stream

                frame_count += 1
                if frame_count >= 200:
                    break
        except KeyboardInterrupt as e:
            print("user stop: ", e)
        except BaseException as e:
            import sys
            sys.print_exception(e)

    # Stop camera
    sensor.stop()
    # Stop encoding
    encoder.Stop(venc_chn)
    # Destroy encoder
    encoder.Destroy(venc_chn)
    # Clean buffer
    MediaManager.deinit()
    print("venc_test stop")

if __name__ == "__main__":
    os.exitpoint(os.EXITPOINT_ENABLE)
    stream_venc_test("/sdcard/examples/test.264", 800, 480)  # VENC encoding data stream example

VENC Module API Manual

Contents

`VENC` Module API Manual#

Overview#

API Introduction#

Encoder.init#

`Encoder.SetOutBufs`#

`Encoder.Create`#

`Encoder.Start`#

`Encoder.SendFrame`#

`Encoder.GetStream`#

`Encoder.ReleaseStream`#

`Encoder.Stop`#

`Encoder.Destroy`#

Data Structure Description#

`ChnAttrStr`#

`StreamData`#

`payload_type`#

`profile`#

`stream_type`#

Example Programs#

Example 1#

Example 2#

VENC Module API Manual

Contents

VENC Module API Manual#

Overview#

API Introduction#

Encoder.__init__#

Encoder.SetOutBufs#

Encoder.Create#

Encoder.Start#

Encoder.SendFrame#

Encoder.GetStream#

Encoder.ReleaseStream#

Encoder.Stop#

Encoder.Destroy#

Data Structure Description#

ChnAttrStr#

StreamData#

payload_type#

profile#

stream_type#

Example Programs#

Example 1#

Example 2#

`VENC` Module API Manual#

Encoder.init#

`Encoder.SetOutBufs`#

`Encoder.Create`#

`Encoder.Start`#

`Encoder.SendFrame`#

`Encoder.GetStream`#

`Encoder.ReleaseStream`#

`Encoder.Stop`#

`Encoder.Destroy`#

`ChnAttrStr`#

`StreamData`#

`payload_type`#

`profile`#

`stream_type`#