1，函数功能
encoder_encode()做的大多是些编码初始工作，比如检查兼容性，初始化av1_lookahead，然后调用av1_get_compressed_data编码，得到压缩后的码流，
2，代码解释,
会在代码中大致说一下这一部分是在干什么，本人还是编码新手，希望多多指正，下一篇会写的详细些
static aom_codec_err_t encoder_encode(aom_codec_alg_priv_t *ctx,
const aom_image_t *img,
aom_codec_pts_t pts,
unsigned long duration,
aom_enc_frame_flags_t enc_flags) {
const size_t kMinCompressedSize = 8192;
volatile aom_codec_err_t res = AOM_CODEC_OK;//用来标识编码是否有错误
AV1_COMP *const cpi = ctx->cpi;
const aom_rational64_t *const timestamp_ratio = &ctx->timestamp_ratio;
volatile aom_codec_pts_t ptsvol = pts;
if (cpi == NULL) return AOM_CODEC_INVALID_PARAM;
//这部分主要将一些初始化的配置从ctx转移到cpi中，为之后的编码做准备
if (img != NULL) {
res = validate_img(ctx, img);
// TODO(jzern) the checks related to cpi's validity should be treated as a
// failure condition, encoder setup is done fully in init() currently.
if (res == AOM_CODEC_OK) {
size_t data_sz = ALIGN_POWER_OF_TWO(ctx->cfg.g_w, 5) * //使value与2的幂对齐
ALIGN_POWER_OF_TWO(ctx->cfg.g_h, 5) * get_image_bps(img);
if (data_sz < kMinCompressedSize) data_sz = kMinCompressedSize;
if (ctx->cx_data == NULL || ctx->cx_data_sz < data_sz) {
ctx->cx_data_sz = data_sz;
free(ctx->cx_data);
ctx->cx_data = (unsigned char *)malloc(ctx->cx_data_sz);
if (ctx->cx_data == NULL) {
return AOM_CODEC_MEM_ERROR;
}
}
}
}
//配置文件
if (ctx->oxcf.mode != GOOD && ctx->oxcf.mode != REALTIME) {
ctx->oxcf.mode = GOOD;
av1_change_config(ctx->cpi, &ctx->oxcf);
}
//偏移量
if (!ctx->pts_offset_initialized) {
ctx->pts_offset = ptsvol;
ctx->pts_offset_initialized = 1;
}
ptsvol -= ctx->pts_offset;
aom_codec_pkt_list_init(&ctx->pkt_list);
volatile aom_enc_frame_flags_t flags = enc_flags;
// The jmp_buf is valid only for the duration of the function that calls
// setjmp(). Therefore, this function must reset the 'setjmp' field to 0
// before it returns.
if (setjmp(cpi->common.error.jmp)) {
cpi->common.error.setjmp = 0;
res = update_error_state(ctx, &cpi->common.error);
aom_clear_system_state();
return res;
}
cpi->common.error.setjmp = 1;
// Note(yunqing): While applying encoding flags, always start from enabling
// all, and then modifying according to the flags. Previous frame's flags are
// overwritten.
/*在应用编码标志时，始终从启用全部开始，然后根据标志进行修改。 前一帧的标志被覆盖。*/
av1_apply_encoding_flags(cpi, flags);////读取flag中的数据
// Handle fixed keyframe intervals
if (ctx->cfg.kf_mode == AOM_KF_AUTO &&
ctx->cfg.kf_min_dist == ctx->cfg.kf_max_dist) {
if (++ctx->fixed_kf_cntr > ctx->cfg.kf_min_dist) {
flags |= AOM_EFLAG_FORCE_KF;
ctx->fixed_kf_cntr = 1;
}
}
if (res == AOM_CODEC_OK) {
int64_t dst_time_stamp = timebase_units_to_ticks(timestamp_ratio, ptsvol);
int64_t dst_end_time_stamp =
timebase_units_to_ticks(timestamp_ratio, ptsvol + duration);
// Set up internal flags
if (ctx->base.init_flags & AOM_CODEC_USE_PSNR) cpi->b_calculate_psnr = 1;
if (img != NULL) {
YV12_BUFFER_CONFIG sd;
res = image2yuvconfig(img, &sd);//把buffer的数据存到sd里
// Store the original flags in to the frame buffer. Will extract the
// key frame flag when we actually encode this frame.
/*将原始标志存储到帧缓冲区中。 当我们实际编码该帧时，将提取关键帧标志。*/
if (av1_receive_raw_frame(cpi, flags | ctx->next_frame_flags, &sd,
dst_time_stamp, dst_end_time_stamp)) {
/*初始化buffer,比如alloc_raw_frame_buffers里会对lookahead结构体里的buffer和变量初始化
*（对每个depth都重新分配buffer,最大深度默认是20），以及alt帧buffer的重新分配。
*init_ref_frame_bufs 初始化cm->ref_frame_map，以及哈希表的映射关系
*alloc_util_frame_buffers初始化source
*lastsource等会每次更新的buffer
*av1_lookahead_push
*/
//初始化失败，错误返回
res = update_error_state(ctx, &cpi->common.error);
}
ctx->next_frame_flags = 0;
}
unsigned char *cx_data = ctx->cx_data;
size_t cx_data_sz = ctx->cx_data_sz;
assert(!(cx_data == NULL && cx_data_sz != 0));
/* 不可见帧内容 */
if (ctx->pending_cx_data) {
memmove(cx_data, ctx->pending_cx_data, ctx->pending_cx_data_sz);
ctx->pending_cx_data = cx_data;
cx_data += ctx->pending_cx_data_sz;
cx_data_sz -= ctx->pending_cx_data_sz;
/* TODO: this is a minimal check, the underlying codec doesn't respect
* the buffer size anyway.
*/
if (cx_data_sz < ctx->cx_data_sz / 2) {
aom_internal_error(&cpi->common.error, AOM_CODEC_ERROR,
"Compressed data buffer too small");
}
}
size_t frame_size = 0;
unsigned int lib_flags = 0;
int is_frame_visible = 0;
int index_size = 0;
int has_fwd_keyframe = 0;
// invisible frames get packed with the next visible frame
// av1_get_compressed_data返回-1指的是没有帧被编码，也是下一层编码的入口
while (cx_data_sz - index_size >= ctx->cx_data_sz / 2 &&
!is_frame_visible &&
-1 != av1_get_compressed_data(cpi, &lib_flags, &frame_size, cx_data,
&dst_time_stamp, &dst_end_time_stamp,
!img, timestamp_ratio)) {
cpi->seq_params_locked = 1;
if (frame_size) {
if (ctx->pending_cx_data == 0) ctx->pending_cx_data = cx_data;
const int write_temporal_delimiter =
!cpi->common.spatial_layer_id && !ctx->pending_frame_count;
if (write_temporal_delimiter) {
uint32_t obu_header_size = 1;
const uint32_t obu_payload_size = 0;
const size_t length_field_size =
aom_uleb_size_in_bytes(obu_payload_size);
if (ctx->pending_cx_data) {
const size_t move_offset = length_field_size + 1;
memmove(ctx->pending_cx_data + move_offset, ctx->pending_cx_data,
frame_size);
}
const uint32_t obu_header_offset = 0;
obu_header_size = av1_write_obu_header(
cpi, OBU_TEMPORAL_DELIMITER, 0,
(uint8_t *)(ctx->pending_cx_data + obu_header_offset));
// OBUs are preceded/succeeded by an unsigned leb128 coded integer.
if (av1_write_uleb_obu_size(obu_header_size, obu_payload_size,
ctx->pending_cx_data) != AOM_CODEC_OK) {
aom_internal_error(&cpi->common.error, AOM_CODEC_ERROR, NULL);
}
frame_size += obu_header_size + obu_payload_size + length_field_size;
}
if (ctx->oxcf.save_as_annexb) {
size_t curr_frame_size = frame_size;
if (av1_convert_sect5obus_to_annexb(cx_data, &curr_frame_size) !=
AOM_CODEC_OK) {
aom_internal_error(&cpi->common.error, AOM_CODEC_ERROR, NULL);
}
frame_size = curr_frame_size;
// B_PRIME (add frame size)
const size_t length_field_size = aom_uleb_size_in_bytes(frame_size);
if (ctx->pending_cx_data) {
const size_t move_offset = length_field_size;
memmove(cx_data + move_offset, cx_data, frame_size);
}
if (av1_write_uleb_obu_size(0, (uint32_t)frame_size, cx_data) !=
AOM_CODEC_OK) {
aom_internal_error(&cpi->common.error, AOM_CODEC_ERROR, NULL);
}
frame_size += length_field_size;
}
ctx->pending_frame_sizes[ctx->pending_frame_count++] = frame_size;
ctx->pending_cx_data_sz += frame_size;
cx_data += frame_size;
cx_data_sz -= frame_size;
index_size = MAG_SIZE * (ctx->pending_frame_count - 1) + 2;
is_frame_visible = cpi->common.show_frame;
has_fwd_keyframe |= (!is_frame_visible &&
cpi->common.current_frame.frame_type == KEY_FRAME);
}
}
if (is_frame_visible) {
// Add the frame packet to the list of returned packets.
aom_codec_cx_pkt_t pkt;
if (ctx->oxcf.save_as_annexb) {
// B_PRIME (add TU size)
size_t tu_size = ctx->pending_cx_data_sz;
const size_t length_field_size = aom_uleb_size_in_bytes(tu_size);
if (ctx->pending_cx_data) {
const size_t move_offset = length_field_size;
memmove(ctx->pending_cx_data + move_offset, ctx->pending_cx_data,
tu_size);
}
if (av1_write_uleb_obu_size(0, (uint32_t)tu_size,
ctx->pending_cx_data) != AOM_CODEC_OK) {
aom_internal_error(&cpi->common.error, AOM_CODEC_ERROR, NULL);
}
ctx->pending_cx_data_sz += length_field_size;
}
pkt.kind = AOM_CODEC_CX_FRAME_PKT;
pkt.data.frame.buf = ctx->pending_cx_data;
pkt.data.frame.sz = ctx->pending_cx_data_sz;
pkt.data.frame.partition_id = -1;
pkt.data.frame.vis_frame_size = frame_size;
pkt.data.frame.pts =
ticks_to_timebase_units(timestamp_ratio, dst_time_stamp) +
ctx->pts_offset;
pkt.data.frame.flags = get_frame_pkt_flags(cpi, lib_flags);
if (has_fwd_keyframe) {
// If one of the invisible frames in the packet is a keyframe, set
// the delayed random access point flag.
pkt.data.frame.flags |= AOM_FRAME_IS_DELAYED_RANDOM_ACCESS_POINT;
}
pkt.data.frame.duration = (uint32_t)ticks_to_timebase_units(
timestamp_ratio, dst_end_time_stamp - dst_time_stamp);
aom_codec_pkt_list_add(&ctx->pkt_list.head, &pkt);
ctx->pending_cx_data = NULL;
ctx->pending_cx_data_sz = 0;
ctx->pending_frame_count = 0;
}
}
cpi->common.error.setjmp = 0;
return res;
}
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