VDEC Module API Manual

Overview

This document provides a detailed introduction to the K230_CanMV VDEC module’s API. This module supports H.264 and H.265 decoding and can be bound to the VO module to output decoded data to VO display devices.

API Introduction

This module provides the Decoder class, which includes the following methods:

Decoder.__init__

Description

Constructor to initialize the decoder instance.

Syntax

decoder = Decoder(type)

Parameters

Parameter Name	Description	Input/Output
type	Encoding type	Input

Return Values

Return Value	Description
Decoder object	Decoder object

Notes

The VDEC module supports up to four concurrent decodings.

Decoder.create

Description

Creates a decoder instance.

Syntax

Decoder.create()

Parameters

None

Return Values

Return Value	Description
None

Decoder.destroy

Description

Destroys the decoder instance.

Syntax

Decoder.destroy()

Parameters

None

Return Values

Return Value	Description
None

Decoder.start

Description

Starts the decoder and begins the decoding process.

Syntax

Decoder.start()

Parameters

None

Return Values

Return Value	Description
None

Decoder.decode

Description

Decodes a frame of data.

Syntax

Decoder.decode(stream_data)

Parameters

Parameter Name	Description	Input/Output
stream_data	Encoded data	Input

Return Values

Return Value	Description
None

Decoder.stop

Description

Releases the current decoded frame’s stream buffer.

Syntax

Decoder.stop()

Parameters

None

Return Values

Return Value	Description
None

Decoder.get_vdec_channel

Description

Return the output channel number of the decoder.

Syntax

Decoder.get_vdec_channel()

Parameters

None

Return Values

Return Value	Description
chn	The output channel number

Decoder.bind_info

Description

Used to get binding information when calling Display.bind_layer.

Syntax

Decoder.bind_info(x = 0, y = 0, width = 1920,height = 1080,pix_format=PIXEL_FORMAT_YUV_SEMIPLANAR_420,chn = 0)

Parameters

Parameter Name	Description	Input/Output
x	The horizontal starting coordinates of the binding area	Input
y	The vertical starting coordinate of the binding area	Input
width	Width of the decoded frame	Input
height	Height of the decoded frame	Input
pix_format	The pixel format of image	Input
chn	Decoding output channel number	Input

Return Values

Return Value	Description
dict object	It includes the source information of the channel, the area size and the pixel format

Data Structure Description

StreamData

Description

Stream structure containing decoded data and its timestamp information.

Definition

class StreamData:
    def __init__(self):
        self.data
        self.pts

Members

Member Name	Description
data	Stream data
pts	Timestamp info

Example Program

Example 1

from media.media import *
from mpp.payload_struct import *
import media.vdecoder as vdecoder
from media.display import *
import time
import os

STREAM_SIZE = 40960

def vdec_test(file_name, width=1280, height=720):
    print("vdec_test start")
    vdec_chn = VENC_CHN_ID_0
    vdec_width = ALIGN_UP(width, 16)
    vdec_height = height
    vdec = None
    vdec_payload_type = K_PT_H264

    # display_type = Display.VIRT
    display_type = Display.ST7701  # Use ST7701 LCD screen for output, max resolution 800*480
    # display_type = Display.LT9611  # Use HDMI for output

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

    # Instantiate video decoder
    vdec = vdecoder.Decoder(vdec_payload_type)

    # Initialize display device
    if display_type == Display.VIRT:
        Display.init(display_type, width=vdec_width, height=vdec_height, fps=30)
    else:
        Display.init(display_type, to_ide=True)

    # Initialize buffer
    MediaManager.init()

    # Create video decoder
    vdec.create()

    # Bind display
    bind_info = vdec.bind_info(width=vdec_width, height=vdec_height, chn=vdec.get_vdec_channel())
    Display.bind_layer(**bind_info, layer=Display.LAYER_VIDEO1)

    vdec.start()

    # Open file
    with open(file_name, "rb") as fi:
        while True:
            os.exitpoint()
            # Read video data stream
            data = fi.read(STREAM_SIZE)
            if not data:
                break
            # Decode data stream
            vdec.decode(data)

    # Stop video decoder
    vdec.stop()
    # Destroy video decoder
    vdec.destroy()
    time.sleep(1)

    # Close display
    Display.deinit()
    # Release buffer
    MediaManager.deinit()

    print("vdec_test stop")

if __name__ == "__main__":
    os.exitpoint(os.EXITPOINT_ENABLE)
    vdec_test("/sdcard/examples/test.264", 800, 480)  # Decode H.264/H.265 video file