avcodec_send_frame和avcodec_receive_packet 作用
相对应avcodec_send_packet | avcodec_receive_frame而言,avcodec_send_frame | avcodec_receive_packet 是编码用的。
int avcodec_send_frame(AVCodecContext *avctx, const AVFrame *frame);
int avcodec_receive_packet(AVCodecContext *avctx, AVPacket *avpkt);
avcodec_send_frame源码
把frame送到avci->buffer_frame中,然后根据avci->buffer_pkt中是否存在编码完成后的cache,判断是否调用encode_receive_packet_internal来编码。
int attribute_align_arg avcodec_send_frame(AVCodecContext *avctx, const AVFrame *frame)
{
AVCodecInternal *avci = avctx->internal;
int ret;
if (!avcodec_is_open(avctx) || !av_codec_is_encoder(avctx->codec))
return AVERROR(EINVAL);
if (avci->draining)
return AVERROR_EOF;
if (avci->buffer_frame->data[0])
return AVERROR(EAGAIN);
if (!frame) {
avci->draining = 1;
} else {
ret = encode_send_frame_internal(avctx, frame);
if (ret < 0)
return ret;
}
if (!avci->buffer_pkt->data && !avci->buffer_pkt->side_data) {
ret = encode_receive_packet_internal(avctx, avci->buffer_pkt);
if (ret < 0 && ret != AVERROR(EAGAIN) && ret != AVERROR_EOF)
return ret;
}
return 0;
}
avcodec_receive_packet 源码
如果avctx->internal->buffer_pkt中存在已经编码后的cache,就用buffer_pkt,不存在就调用encode_receive_packet_internal编码。
int attribute_align_arg avcodec_receive_packet(AVCodecContext *avctx, AVPacket *avpkt)
{
AVCodecInternal *avci = avctx->internal;
int ret;
av_packet_unref(avpkt);
if (!avcodec_is_open(avctx) || !av_codec_is_encoder(avctx->codec))
return AVERROR(EINVAL);
if (avci->buffer_pkt->data || avci->buffer_pkt->side_data) {
av_packet_move_ref(avpkt, avci->buffer_pkt);
} else {
ret = encode_receive_packet_internal(avctx, avpkt);
if (ret < 0)
return ret;
}
return 0;
}
encode_send_frame_internal源码
主要作用是把输入的AVFrame复制到avctx->internal->buffer_frame中。
如果是音频,还会根据codec的capabilities类型,判断输入的AVFrame的采样数量是否足够,不足够就返回AVERROR(EINVAL)。
static int encode_send_frame_internal(AVCodecContext *avctx, const AVFrame *src)
{
AVCodecInternal *avci = avctx->internal;
AVFrame *dst = avci->buffer_frame;
int ret;
if (avctx->codec->type == AVMEDIA_TYPE_AUDIO) {
AVFrameSideData *sd = av_frame_get_side_data(src, AV_FRAME_DATA_AUDIO_SERVICE_TYPE);
if (sd && sd->size >= sizeof(enum AVAudioServiceType))
avctx->audio_service_type = *(enum AVAudioServiceType*)sd->data;
if (avctx->codec->capabilities & AV_CODEC_CAP_SMALL_LAST_FRAME) {
if (src->nb_samples > avctx->frame_size) {
av_log(avctx, AV_LOG_ERROR, "more samples than frame size\n");
return AVERROR(EINVAL);
}
} else if (!(avctx->codec->capabilities & AV_CODEC_CAP_VARIABLE_FRAME_SIZE)) {
if (avctx->internal->last_audio_frame) {
av_log(avctx, AV_LOG_ERROR, "frame_size (%d) was not respected for a non-last frame\n", avctx->frame_size);
return AVERROR(EINVAL);
}
if (src->nb_samples < avctx->frame_size) {
ret = pad_last_frame(avctx, dst, src);
if (ret < 0)
return ret;
avctx->internal->last_audio_frame = 1;
} else if (src->nb_samples > avctx->frame_size) {
av_log(avctx, AV_LOG_ERROR, "nb_samples (%d) != frame_size (%d)\n", src->nb_samples, avctx->frame_size);
return AVERROR(EINVAL);
}
}
}
if (!dst->data[0]) {
ret = av_frame_ref(dst, src);
if (ret < 0)
return ret;
}
return 0;
}
encode_receive_packet_internal 源码
编码阶段重要函数,这个函数会判断所使用的AVCodec是否已经实现了receive_packet函数,从而判断是否是调用receive_packet编码还是调用encode_simple_receive_packet编码。
static int encode_receive_packet_internal(AVCodecContext *avctx, AVPacket *avpkt)
{
AVCodecInternal *avci = avctx->internal;
int ret;
if (avci->draining_done)
return AVERROR_EOF;
av_assert0(!avpkt->data && !avpkt->side_data);
if (avctx->codec->type == AVMEDIA_TYPE_VIDEO) {
if ((avctx->flags & AV_CODEC_FLAG_PASS1) && avctx->stats_out)
avctx->stats_out[0] = '\0';
if (av_image_check_size2(avctx->width, avctx->height, avctx->max_pixels, AV_PIX_FMT_NONE, 0, avctx))
return AVERROR(EINVAL);
}
if (avctx->codec->receive_packet) {
ret = avctx->codec->receive_packet(avctx, avpkt);
if (ret < 0)
av_packet_unref(avpkt);
else
av_assert0(!avpkt->data || avpkt->buf);
} else
ret = encode_simple_receive_packet(avctx, avpkt);
if (ret == AVERROR_EOF)
avci->draining_done = 1;
return ret;
}
encode_simple_receive_packet 源码
这个函数通过while循环不停的调用encode_simple_internal编码。
static int encode_simple_receive_packet(AVCodecContext *avctx, AVPacket *avpkt)
{
int ret;
while (!avpkt->data && !avpkt->side_data) {
ret = encode_simple_internal(avctx, avpkt);
if (ret < 0)
return ret;
}
return 0;
}
encode_simple_internal源码
软编码的大部分都会调用到这个函数中,在这种函数中,通过判断是否是多线程编码,调用不同的编码函数。
static int encode_simple_internal(AVCodecContext *avctx, AVPacket *avpkt)
{
AVCodecInternal *avci = avctx->internal;
EncodeSimpleContext *es = &avci->es;
AVFrame *frame = es->in_frame;
int got_packet;
int ret;
if (avci->draining_done)
return AVERROR_EOF;
if (!frame->buf[0] && !avci->draining) {
av_frame_unref(frame);
ret = ff_encode_get_frame(avctx, frame);
if (ret < 0 && ret != AVERROR_EOF)
return ret;
}
if (!frame->buf[0]) {
if (!(avctx->codec->capabilities & AV_CODEC_CAP_DELAY ||
(avci->frame_thread_encoder && avctx->active_thread_type & FF_THREAD_FRAME)))
return AVERROR_EOF;
frame = NULL;
}
got_packet = 0;
av_assert0(avctx->codec->encode2);
if (CONFIG_FRAME_THREAD_ENCODER &&
avci->frame_thread_encoder && (avctx->active_thread_type & FF_THREAD_FRAME))
ret = ff_thread_video_encode_frame(avctx, avpkt, frame, &got_packet);
else {
ret = avctx->codec->encode2(avctx, avpkt, frame, &got_packet);
if (avctx->codec->type == AVMEDIA_TYPE_VIDEO && !ret && got_packet &&
!(avctx->codec->capabilities & AV_CODEC_CAP_DELAY))
avpkt->pts = avpkt->dts = frame->pts;
}
av_assert0(ret <= 0);
emms_c();
if (!ret && got_packet) {
if (avpkt->data) {
ret = av_packet_make_refcounted(avpkt);
if (ret < 0)
goto end;
}
if (frame && !(avctx->codec->capabilities & AV_CODEC_CAP_DELAY)) {
if (avctx->codec->type == AVMEDIA_TYPE_AUDIO) {
if (avpkt->pts == AV_NOPTS_VALUE)
avpkt->pts = frame->pts;
if (!avpkt->duration)
avpkt->duration = ff_samples_to_time_base(avctx,
frame->nb_samples);
}
}
if (avctx->codec->type == AVMEDIA_TYPE_AUDIO) {
avpkt->flags |= AV_PKT_FLAG_KEY;
avpkt->dts = avpkt->pts;
}
}
if (avci->draining && !got_packet)
avci->draining_done = 1;
end:
if (ret < 0 || !got_packet)
av_packet_unref(avpkt);
if (frame) {
if (!ret)
avctx->frame_number++;
av_frame_unref(frame);
}
if (got_packet)
av_assert0(!avpkt->data || avpkt->buf);
return ret;
}
ff_thread_video_encode_frame 源码
多线程编码,配合调用avcodec_open2 时,打开的编码线程。
int ff_thread_video_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
AVFrame *frame, int *got_packet_ptr)
{
ThreadContext *c = avctx->internal->frame_thread_encoder;
Task *outtask;
av_assert1(!*got_packet_ptr);
if(frame){
av_frame_move_ref(c->tasks[c->task_index].indata, frame);
pthread_mutex_lock(&c->task_fifo_mutex);
c->task_index = (c->task_index + 1) % c->max_tasks;
pthread_cond_signal(&c->task_fifo_cond);
pthread_mutex_unlock(&c->task_fifo_mutex);
}
outtask = &c->tasks[c->finished_task_index];
pthread_mutex_lock(&c->finished_task_mutex);
if (c->task_index == c->finished_task_index ||
(frame && !outtask->finished &&
(c->task_index - c->finished_task_index + c->max_tasks) % c->max_tasks <= avctx->thread_count)) {
pthread_mutex_unlock(&c->finished_task_mutex);
return 0;
}
while (!outtask->finished) {
pthread_cond_wait(&c->finished_task_cond, &c->finished_task_mutex);
}
pthread_mutex_unlock(&c->finished_task_mutex);
outtask->finished = 0;
av_packet_move_ref(pkt, outtask->outdata);
if(pkt->data)
*got_packet_ptr = 1;
c->finished_task_index = (c->finished_task_index + 1) % c->max_tasks;
return outtask->return_code;
}
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