Functions and Restrictions
Function Usage
Video Decoder (VDEC) decodes videos. After internal VPC processing, VDEC outputs images in specified formats. For details, see Restrictions on Stream/Image Formats, Width and Height Alignment, and Buffers.
Resolution Restrictions
- Input resolution range:
Version
Resolution Range
Atlas training products Atlas inference products Atlas A2 training products /Atlas A2 inference products Atlas A3 training products /Atlas A3 inference products 128 x 128 to 4096 x 4096
Atlas 200I/500 A2 inference products H.264 input streams: 128 x 128 to 8192 x 8192
H.265 input streams: 128 x 128 to 5400 x 8192
- Output resolution range:
Version
Resolution Range
Atlas training products Atlas inference products Atlas A2 training products /Atlas A2 inference products Atlas A3 training products /Atlas A3 inference products 10 x 6 to 4096 x 4096
Atlas 200I/500 A2 inference products The maximum resolution of the output image is 8192 x 8192. When the width of the input stream is less than or equal to 4096, the minimum resolution of the output image is 10 x 6. Otherwise, the minimum resolution of the output image is 128 x 128.
Restrictions on Stream/Image Formats, Width and Height Alignment, and Buffers
In terms of the VDEC function, the input/output buffer lifetime is managed by the user.
- Input buffer
Call acl.media.dvpp_malloc/acl.media.dvpp_free or acl.rt.malloc/acl.rt.free to allocate or free the buffer. The buffer size is the size of space occupied by actual input streams.
The buffer allocated by calling acl.media.dvpp_malloc is dedicated for processing media data. However, the address space of the dedicated buffer is limited. If buffer planning is considered or resources are limited, you are advised to call acl.rt.malloc for allocation when using the VDEC function.
- Output buffer
Call acl.media.dvpp_malloc or acl.media.dvpp_free to allocate or free the buffer. For details about the buffer size, see the formula in the following table.
For details about the definition of the output image format, see acldvppPixelFormat. For details about the concepts such as width stride and height stride, see Terminology.
- H.264 BP/MP/HP level 5.1 YUV420 streams (Annex-B raw video streams only)
- H.265 8-/10-bit level 5.1 YUV420 streams (Annex-B raw video streams only)
The following table describes the requirements on the output image format and alignment of width and height during VDEC video decoding.
Version |
Output Format |
Output Width and Height |
Output Width Stride, Height Stride, and Buffer Size |
Output Width Stride, Height Stride, and Buffer Size |
|---|---|---|---|---|
General format, supported by all versions |
YUV420SP NV12 8bit |
Width: Must be a multiple of 2. Height: Must be a multiple of 2. |
Width stride: Round up the width to the nearest multiple of 16. If the configured width of the output image is less than 16, the minimum width stride must be at least 32. Height stride: Round up the height to the nearest multiple of 2. Buffer size (in bytes) ≥ Width stride x Height stride x 3/2 |
Width stride: No alignment requirement. The value is the same as width and ranges from 10 to 24576. Height stride: No alignment requirement. The value is the same as height and ranges from 6 to 24576. Buffer size (in bytes) ≥ Width stride x Height stride x 3/2 |
YUV420SP NV21 8bit |
||||
Only the following versions support this format: |
RGB888 |
No alignment requirement. |
Width stride: Round up the width to the nearest multiple of 16 and multiply the result by 3. Height stride: No alignment requirement. Buffer size (in bytes) ≥ Width stride x Height stride |
Width stride = Width x 3. The value ranges from 30 to 24576. Height stride: No alignment requirement. The value range from 6 to 24576. Buffer size (in bytes) ≥ Width stride x Height stride |
BGR888 |
Other Restrictions
- VDEC decodes input streams frame by frame.
- Bad frames or frame loss in the streams may cause VDEC frame loss.
- VDEC decodes only the H.264 8-bit streams encoded in interlaced mode.