vdec_get_frame

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

Fetches the decoded image and input stream of a decoding channel.

During JPEGD image decoding, if hardware decoding fails when this API is called, software decoding is triggered within this API.

Prototype

C Prototype

        
             hi_s32 hi_mpi_vdec_get_frame(hi_vdec_chn chn, hi_video_frame_info *frame_info, hi_vdec_supplement_info *supplement, hi_vdec_stream *stream, hi_s32 milli_sec)

Python Function

        
             frame_info, supplement, stream, ret = acl.himpi.vdec_get_frame(chn, milli_sec)

Parameters

Parameter	Description
chn	Int, decoding channel ID.
milli_sec	Int, timeout interval, in milliseconds. -1: blocking mode. 0: non-blocking mode. > 0: timeout interval (timeout mode). The timeout interval varies with the operating system. The deviation is generally within a time slice of an operating system. For example, if the time slice of an operating system is 4 ms and the value of milli_sec is set to 1, the actual timeout interval ranges from 1 ms to 5 ms. When the CPU load is high, the timeout interval may fluctuate. NOTE: In the JPEGD image decoding scenario, the timeout interval configured here refers only to the wait time for obtaining the hardware decoding result, excluding the software decoding time.

Parameter

Description

chn

Int, decoding channel ID.

milli_sec

Int, timeout interval, in milliseconds.

-1: blocking mode.
0: non-blocking mode.
> 0: timeout interval (timeout mode). The timeout interval varies with the operating system. The deviation is generally within a time slice of an operating system. For example, if the time slice of an operating system is 4 ms and the value of milli_sec is set to 1, the actual timeout interval ranges from 1 ms to 5 ms. When the CPU load is high, the timeout interval may fluctuate.
NOTE:

In the JPEGD image decoding scenario, the timeout interval configured here refers only to the wait time for obtaining the hardware decoding result, excluding the software decoding time.

Return Value

Return Value	Description
frame_info	Dict, pointer to information about decoded images. The decoded data is stored in the device memory. For details, see hi_video_frame_info.
supplement	Dict, supplementary information about the decoded images. This parameter is reserved. .
stream	Dict, dictionary of information about the decoded input stream. For details, see hi_vdec_stream.
ret	Int, error code. 0: success. After the decoded data is obtained successfully, acl.himpi.vdec_release_frame needs to be called to release decoding resources. Although success message is returned, the fetched data may be the result of decoding failure. To check the decode success or failure result, query the frame_flag parameter of hi_video_frame (a member of hi_video_frame_info). Other values indicate failure. For details, see VDEC/JPEGD Return Codes. NOTE: If no channel is created during image decoding, the error code HI_ERR_VDEC_UNEXIST is returned. If the channel is destroyed in the image fetching process, the error code HI_ERR_VDEC_UNEXIST is returned. If the channel is reset in the image fetching process, the error code HI_ERR_VDEC_UNEXIST is returned. In non-blocking mode, if the buffer has no decoded images, the error code HI_ERR_VDEC_BUF_EMPTY is returned. In timeout mode, if no hardware decoding result is obtained within the specified timeout interval, the error code HI_ERR_VDEC_BUF_EMPTY is returned. In this case, increase the timeout interval or call this API repeatedly to obtain the decoding result.

Restrictions

This API fetches the VDEC result, including the input buffer and output buffer.
For decoding of JPEG(420), JPEG(422), or JPEG(440) input images, if the input width and height are odd numbers, the output width and height are rounded down to the nearest multiples of 2 by default. For decoding of JPEG(444) or JPEG(400) input images, the output width and height are consistent with the input width and height by default. To adjust the width and height alignment mode of the output image, call the acl.himpi.vdec_set_jpegd_precision_mode API.

Reference

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

Parent topic: VDEC/JPEGD APIs