/* SPDX-License-Identifier: BSD-2-Clause */
/*
 * h264_nal_synth.h — synthesise AnnexB SPS + PPS NAL units from the
 * v4l2_ctrl_h264_sps / v4l2_ctrl_h264_pps structures the libva driver
 * sets via V4L2 stateless controls and the daedalus kernel module
 * forwards over the chardev as struct daedalus_h264_meta.
 *
 * libavcodec needs SPS+PPS NAL units BEFORE any slice NAL to bind
 * the slice's pic_parameter_set_id reference; libva-v4l2-request
 * passes only the slice in the OUTPUT buffer (per the V4L2 stateless
 * H.264 contract).  The daemon bridges by reconstructing SPS+PPS
 * NAL bytes from the structured controls and prepending them to the
 * bitstream the daemon hands libavcodec.
 *
 * Output is AnnexB-framed: 0x00 0x00 0x00 0x01 start code + NAL.
 * Emulation prevention (insert 0x03 after any 0x00 0x00 in the RBSP)
 * is handled by this module so the consumer can concatenate raw.
 */
#ifndef DAEDALUS_H264_NAL_SYNTH_H
#define DAEDALUS_H264_NAL_SYNTH_H

#include <stddef.h>
#include <stdint.h>

#include <linux/v4l2-controls.h>

/*
 * Encode an AnnexB SPS NAL into out[].  Returns the number of bytes
 * written, or 0 on overflow / malformed input.  out_cap must be at
 * least 256 bytes to handle worst-case SPS with full offset_for_ref_
 * frame[] cycle.
 */
size_t h264_synth_sps(const struct v4l2_ctrl_h264_sps *sps,
		      uint8_t *out, size_t out_cap);

/*
 * Encode an AnnexB PPS NAL into out[].  Returns the number of bytes
 * written, or 0 on overflow.  out_cap should be at least 64 bytes;
 * PPS NALs are small.
 */
size_t h264_synth_pps(const struct v4l2_ctrl_h264_pps *pps,
		      uint8_t *out, size_t out_cap);

#endif /* DAEDALUS_H264_NAL_SYNTH_H */