UM0851 datasheet(156/245 Pages) STMICROELECTRONICS

156 / 245 page

Accelerator engine device drivers

UM0851

156/245

Doc ID 16604 Rev 2

On success, zero is returned, otherwise on error, -1 is returned and errno is set

appropriately.

After completion of processing, if user needs to encode/decode another image, then user

don't have to close JPEG nodes, de-allocate buffer memory and open the nodes again. User

can simply call this function again with size of new input data. This resets complete JPEG

system (software and hardware).

Set JPEG Info

JPEG can perform four types of operations. They are:

●

Encoding with header processing (EWH): Output JPEG image will have header as part

of image.

●

Encoding without header processing (EWOH): Output JPEG image will not have

header as part of image.

●

Decoding with header processing (DWH): Input JPEG image will have header as part

of image.

●

Decoding without header processing (DWOH): Input JPEG image will not have header

as part of image.

You need to pass JPEG header and compression table information to JPEG driver in all

above cases, except DWH. In DWH JPEG codec extracts header and table information from

input JPEG image. Before proceeding with encoding/decoding, you will provide header and

table information to JPEG driver (not required for DWH).

Use the following system call to set JPEG info for EWH and EWOH:

ioctl(wfd, JPEGIOC_SET_ENC_INFO, &enc_info);

wfd: file descriptor of jpeg write node.

JPEGIOC_SET_ENC_INFO: ioctl command for setting JPEG encoding information.

enc_info: structure containing jpeg encoding information.

Description of enc_info structure:

struct jpeg_enc_info {

struct jpeg_hdr hdr;/* jpeg image header */

int hdr_enable; /* header processing enable/disable */

char qnt_mem[QNT_MEM_SIZE]; /* quantization memory */

char dht_mem[DHT_MEM_SIZE]; /* DHT memory */

char henc_mem[HENC_MEM_SIZE]; /* Huff enc memory */

};

Description of jpeg_hdr structure:

struct jpeg_hdr {

u32 num_clr_cmp;

/* number of color components minus 1. */

u32 clr_spc_type; /* number of quantization tables in the output stream. */

u32 num_cmp_for_scan_hdr; /* number of components for scan

header marker segment

minus 1.*/

u32 rst_mark_en;/* restart marker enable/disable */

u32 xsize; /* number of pixels per line */

u32 ysize; /* number of lines. */

u32 mcu_num; /* this value defines the number of minimum coded units to be coded,

minus 1 */

u32 mcu_num_in_rst; /* number of mcu's between two restart markers minus 1.*/

struct mcu_composition mcu_comp[MAX_MCU_COMP]; /* represents MCU composition */

};

Description of mcu_composition structure:

struct mcu_composition {

UM0851 Datasheet(PDF) 156 Page - STMicroelectronics

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