ijkplayer框架簡析 -- avcodec_decode_video2

int attribute_align_arg avcodec_decode_video2(AVCodecContext *avctx, AVFrame *picture,
int *got_picture_ptr,
const AVPacket *avpkt)
{
return compat_decode(avctx, picture, got_picture_ptr, avpkt);
}

static int compat_decode(AVCodecContext *avctx, AVFrame *frame,
int *got_frame, const AVPacket *pkt)
{
AVCodecInternal *avci = avctx->internal;
int ret = 0;

av_assert0(avci->compat_decode_consumed == 0);

*got_frame = 0;
avci->compat_decode = 1;

if (avci->compat_decode_partial_size > 0 &&
avci->compat_decode_partial_size != pkt->size) {
av_log(avctx, AV_LOG_ERROR,
"Got unexpected packet size after a partial decode\n");
ret = AVERROR(EINVAL);
goto finish;
}

if (!avci->compat_decode_partial_size) {
ret = avcodec_send_packet(avctx, pkt);
if (ret == AVERROR_EOF)
ret = 0;
else if (ret == AVERROR(EAGAIN)) {
/* we fully drain all the output in each decode call, so this should not
* ever happen */
ret = AVERROR_BUG;
goto finish;
} else if (ret < 0)
goto finish;
}

while (ret >= 0) {
ret = avcodec_receive_frame(avctx, frame);
if (ret < 0) {
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
ret = 0;
goto finish;
}

if (frame != avci->compat_decode_frame) {
if (!avctx->refcounted_frames) {
ret = unrefcount_frame(avci, frame);
if (ret < 0)
goto finish;
}

*got_frame = 1;
frame = avci->compat_decode_frame;
} else {
if (!avci->compat_decode_warned) {
av_log(avctx, AV_LOG_WARNING, "The deprecated avcodec_decode_* "
"API cannot return all the frames for this decoder. "
"Some frames will be dropped. Update your code to the "
"new decoding API to fix this.\n");
avci->compat_decode_warned = 1;
}
}

if (avci->draining || (!avctx->codec->bsfs && avci->compat_decode_consumed < pkt->size))
break;
}

finish:
if (ret == 0) {
/* if there are any bsfs then assume full packet is always consumed */
if (avctx->codec->bsfs)
ret = pkt->size;
else
ret = FFMIN(avci->compat_decode_consumed, pkt->size);
}
avci->compat_decode_consumed = 0;
avci->compat_decode_partial_size = (ret >= 0) ? pkt->size - ret : 0;

return ret;
}

int attribute_align_arg avcodec_send_packet(AVCodecContext *avctx, const AVPacket *avpkt)
{
AVCodecInternal *avci = avctx->internal;
int ret;

if (!avcodec_is_open(avctx) || !av_codec_is_decoder(avctx->codec))
return AVERROR(EINVAL);

if (avctx->internal->draining)
return AVERROR_EOF;

if (avpkt && !avpkt->size && avpkt->data)
return AVERROR(EINVAL);

ret = bsfs_init(avctx);
if (ret < 0)
return ret;

av_packet_unref(avci->buffer_pkt);
if (avpkt && (avpkt->data || avpkt->side_data_elems)) {
ret = av_packet_ref(avci->buffer_pkt, avpkt);
if (ret < 0)
return ret;
}

ret = av_bsf_send_packet(avci->filter.bsfs[0], avci->buffer_pkt);
if (ret < 0) {
av_packet_unref(avci->buffer_pkt);
return ret;
}

if (!avci->buffer_frame->buf[0]) {
ret = decode_receive_frame_internal(avctx, avci->buffer_frame);
if (ret < 0 && ret != AVERROR(EAGAIN) && ret != AVERROR_EOF)
return ret;
}

return 0;
}

static int decode_receive_frame_internal(AVCodecContext *avctx, AVFrame *frame)
{
AVCodecInternal *avci = avctx->internal;
int ret;

av_assert0(!frame->buf[0]);

if (avctx->codec->receive_frame)
ret = avctx->codec->receive_frame(avctx, frame);
else
ret = decode_simple_receive_frame(avctx, frame);

if (ret == AVERROR_EOF)
avci->draining_done = 1;

return ret;
}

static int decode_simple_receive_frame(AVCodecContext *avctx, AVFrame *frame)
{
int ret;

while (!frame->buf[0]) {
ret = decode_simple_internal(avctx, frame);
if (ret < 0)
return ret;
}

return 0;
}

/*
 * The core of the receive_frame_wrapper for the decoders implementing
 * the simple API. Certain decoders might consume partial packets without
 * returning any output, so this function needs to be called in a loop until it
 * returns EAGAIN.
 **/
static int decode_simple_internal(AVCodecContext *avctx, AVFrame *frame)
{
AVCodecInternal*avci = avctx->internal;
DecodeSimpleContext *ds = &avci->ds;
AVPacket*pkt = ds->in_pkt;
// copy to ensure we do not change pkt
AVPacket tmp;
int got_frame, actual_got_frame, did_split;
int ret;

if (!pkt->data && !avci->draining) {
av_packet_unref(pkt);
ret = ff_decode_get_packet(avctx, pkt);
if (ret < 0 && ret != AVERROR_EOF)
return ret;
}

// Some codecs (at least wma lossless) will crash when feeding drain packets
// after EOF was signaled.
if (avci->draining_done)
return AVERROR_EOF;

if (!pkt->data &&
!(avctx->codec->capabilities & AV_CODEC_CAP_DELAY ||
avctx->active_thread_type & FF_THREAD_FRAME))
return AVERROR_EOF;

tmp = *pkt;
#if FF_API_MERGE_SD
FF_DISABLE_DEPRECATION_WARNINGS
did_split = avci->compat_decode_partial_size ?
ff_packet_split_and_drop_side_data(&tmp) :
av_packet_split_side_data(&tmp);

if (did_split) {
ret = extract_packet_props(avctx->internal, &tmp);
if (ret < 0)
return ret;

ret = apply_param_change(avctx, &tmp);
if (ret < 0)
return ret;
}
FF_ENABLE_DEPRECATION_WARNINGS
#endif

got_frame = 0;

if (HAVE_THREADS && avctx->active_thread_type & FF_THREAD_FRAME) {
ret = ff_thread_decode_frame(avctx, frame, &got_frame, &tmp);
} else {
ret = avctx->codec->decode(avctx, frame, &got_frame, &tmp);

if (!(avctx->codec->caps_internal & FF_CODEC_CAP_SETS_PKT_DTS))
frame->pkt_dts = pkt->dts;
if (avctx->codec->type == AVMEDIA_TYPE_VIDEO) {
if(!avctx->has_b_frames)
frame->pkt_pos = pkt->pos;
//FIXME these should be under if(!avctx->has_b_frames)
/* get_buffer is supposed to set frame parameters */
if (!(avctx->codec->capabilities & AV_CODEC_CAP_DR1)) {
if (!frame->sample_aspect_ratio.num)frame->sample_aspect_ratio = avctx->sample_aspect_ratio;
if (!frame->width)frame->width= avctx->width;
if (!frame->height)frame->height= avctx->height;
if (frame->format == AV_PIX_FMT_NONE) frame->format= avctx->pix_fmt;
}
}
}
emms_c();
actual_got_frame = got_frame;

if (avctx->codec->type == AVMEDIA_TYPE_VIDEO) {
if (frame->flags & AV_FRAME_FLAG_DISCARD)
got_frame = 0;
if (got_frame)
frame->best_effort_timestamp = guess_correct_pts(avctx,
frame->pts,
frame->pkt_dts);
} else if (avctx->codec->type == AVMEDIA_TYPE_AUDIO) {
uint8_t *side;
int side_size;
uint32_t discard_padding = 0;
uint8_t skip_reason = 0;
uint8_t discard_reason = 0;

if (ret >= 0 && got_frame) {
frame->best_effort_timestamp = guess_correct_pts(avctx,
frame->pts,
frame->pkt_dts);
if (frame->format == AV_SAMPLE_FMT_NONE)
frame->format = avctx->sample_fmt;
if (!frame->channel_layout)
frame->channel_layout = avctx->channel_layout;
if (!frame->channels)
frame->channels = avctx->channels;
if (!frame->sample_rate)
frame->sample_rate = avctx->sample_rate;
}

side= av_packet_get_side_data(avci->last_pkt_props, AV_PKT_DATA_SKIP_SAMPLES, &side_size);
if(side && side_size>=10) {
avctx->internal->skip_samples = AV_RL32(side) * avctx->internal->skip_samples_multiplier;
discard_padding = AV_RL32(side + 4);
av_log(avctx, AV_LOG_DEBUG, "skip %d / discard %d samples due to side data\n",
avctx->internal->skip_samples, (int)discard_padding);
skip_reason = AV_RL8(side + 8);
discard_reason = AV_RL8(side + 9);
}

if ((frame->flags & AV_FRAME_FLAG_DISCARD) && got_frame &&
!(avctx->flags2 & AV_CODEC_FLAG2_SKIP_MANUAL)) {
avctx->internal->skip_samples = FFMAX(0, avctx->internal->skip_samples - frame->nb_samples);
got_frame = 0;
}

if (avctx->internal->skip_samples > 0 && got_frame &&
!(avctx->flags2 & AV_CODEC_FLAG2_SKIP_MANUAL)) {
if(frame->nb_samples <= avctx->internal->skip_samples){
got_frame = 0;
avctx->internal->skip_samples -= frame->nb_samples;
av_log(avctx, AV_LOG_DEBUG, "skip whole frame, skip left: %d\n",
avctx->internal->skip_samples);
} else {
av_samples_copy(frame->extended_data, frame->extended_data, 0, avctx->internal->skip_samples,
frame->nb_samples - avctx->internal->skip_samples, avctx->channels, frame->format);
if(avctx->pkt_timebase.num && avctx->sample_rate) {
int64_t diff_ts = av_rescale_q(avctx->internal->skip_samples,
(AVRational){1, avctx->sample_rate},
avctx->pkt_timebase);
if(frame->pts!=AV_NOPTS_VALUE)
frame->pts += diff_ts;
#if FF_API_PKT_PTS
FF_DISABLE_DEPRECATION_WARNINGS
if(frame->pkt_pts!=AV_NOPTS_VALUE)
frame->pkt_pts += diff_ts;
FF_ENABLE_DEPRECATION_WARNINGS
#endif
if(frame->pkt_dts!=AV_NOPTS_VALUE)
frame->pkt_dts += diff_ts;
if (frame->pkt_duration >= diff_ts)
frame->pkt_duration -= diff_ts;
} else {
av_log(avctx, AV_LOG_WARNING, "Could not update timestamps for skipped samples.\n");
}
av_log(avctx, AV_LOG_DEBUG, "skip %d/%d samples\n",
avctx->internal->skip_samples, frame->nb_samples);
frame->nb_samples -= avctx->internal->skip_samples;
avctx->internal->skip_samples = 0;
}
}

if (discard_padding > 0 && discard_padding <= frame->nb_samples && got_frame &&
!(avctx->flags2 & AV_CODEC_FLAG2_SKIP_MANUAL)) {
if (discard_padding == frame->nb_samples) {
got_frame = 0;
} else {
if(avctx->pkt_timebase.num && avctx->sample_rate) {
int64_t diff_ts = av_rescale_q(frame->nb_samples - discard_padding,
(AVRational){1, avctx->sample_rate},
avctx->pkt_timebase);
frame->pkt_duration = diff_ts;
} else {
av_log(avctx, AV_LOG_WARNING, "Could not update timestamps for discarded samples.\n");
}
av_log(avctx, AV_LOG_DEBUG, "discard %d/%d samples\n",
(int)discard_padding, frame->nb_samples);
frame->nb_samples -= discard_padding;
}
}

if ((avctx->flags2 & AV_CODEC_FLAG2_SKIP_MANUAL) && got_frame) {
AVFrameSideData *fside = av_frame_new_side_data(frame, AV_FRAME_DATA_SKIP_SAMPLES, 10);
if (fside) {
AV_WL32(fside->data, avctx->internal->skip_samples);
AV_WL32(fside->data + 4, discard_padding);
AV_WL8(fside->data + 8, skip_reason);
AV_WL8(fside->data + 9, discard_reason);
avctx->internal->skip_samples = 0;
}
}
}
#if FF_API_MERGE_SD
if (did_split) {
av_packet_free_side_data(&tmp);
if(ret == tmp.size)
ret = pkt->size;
}
#endif

if (avctx->codec->type == AVMEDIA_TYPE_AUDIO &&
!avci->showed_multi_packet_warning &&
ret >= 0 && ret != pkt->size && !(avctx->codec->capabilities & AV_CODEC_CAP_SUBFRAMES)) {
av_log(avctx, AV_LOG_WARNING, "Multiple frames in a packet.\n");
avci->showed_multi_packet_warning = 1;
}

if (!got_frame)
av_frame_unref(frame);

if (ret >= 0 && avctx->codec->type == AVMEDIA_TYPE_VIDEO && !(avctx->flags & AV_CODEC_FLAG_TRUNCATED))
ret = pkt->size;

#if FF_API_AVCTX_TIMEBASE
if (avctx->framerate.num > 0 && avctx->framerate.den > 0)
avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
#endif

/* do not stop draining when actual_got_frame != 0 or ret < 0 */
/* got_frame == 0 but actual_got_frame != 0 when frame is discarded */
if (avctx->internal->draining && !actual_got_frame) {
if (ret < 0) {
/* prevent infinite loop if a decoder wrongly always return error on draining */
/* reasonable nb_errors_max = maximum b frames + thread count */
int nb_errors_max = 20 + (HAVE_THREADS && avctx->active_thread_type & FF_THREAD_FRAME ?
avctx->thread_count : 1);

if (avci->nb_draining_errors++ >= nb_errors_max) {
av_log(avctx, AV_LOG_ERROR, "Too many errors when draining, this is a bug. "
"Stop draining and force EOF.\n");
avci->draining_done = 1;
ret = AVERROR_BUG;
}
} else {
avci->draining_done = 1;
}
}

avci->compat_decode_consumed += ret;

if (ret >= pkt->size || ret < 0) {
av_packet_unref(pkt);
} else {
int consumed = ret;

pkt->data+= consumed;
pkt->size-= consumed;
avci->last_pkt_props->size -= consumed; // See extract_packet_props() comment.
pkt->pts= AV_NOPTS_VALUE;
pkt->dts= AV_NOPTS_VALUE;
avci->last_pkt_props->pts = AV_NOPTS_VALUE;
avci->last_pkt_props->dts = AV_NOPTS_VALUE;
}

if (got_frame)
av_assert0(frame->buf[0]);

return ret < 0 ? ret : 0;
}

AVCodec ff_h264_decoder = {
.name= "h264",
.long_name= NULL_IF_CONFIG_SMALL("H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10"),
.type= AVMEDIA_TYPE_VIDEO,
.id= AV_CODEC_ID_H264,
.priv_data_size= sizeof(H264Context),
.init= h264_decode_init,
.close= h264_decode_end,
.decode= h264_decode_frame,
.capabilities= /*AV_CODEC_CAP_DRAW_HORIZ_BAND |*/ AV_CODEC_CAP_DR1 |
AV_CODEC_CAP_DELAY | AV_CODEC_CAP_SLICE_THREADS |
AV_CODEC_CAP_FRAME_THREADS,
.caps_internal= FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_EXPORTS_CROPPING,
.flush= flush_dpb,
.init_thread_copy= ONLY_IF_THREADS_ENABLED(decode_init_thread_copy),
.update_thread_context = ONLY_IF_THREADS_ENABLED(ff_h264_update_thread_context),
.profiles= NULL_IF_CONFIG_SMALL(ff_h264_profiles),
.priv_class= &h264_class,
};

static int h264_decode_frame(AVCodecContext *avctx, void *data,
int *got_frame, AVPacket *avpkt)
{
const uint8_t *buf = avpkt->data;
int buf_size= avpkt->size;
H264Context *h= avctx->priv_data;
AVFrame *pict= data;
int buf_index;
int ret;

h->flags = avctx->flags;
h->setup_finished = 0;
h->nb_slice_ctx_queued = 0;

ff_h264_unref_picture(h, &h->last_pic_for_ec);

/* end of stream, output what is still in the buffers */
if (buf_size == 0)
return send_next_delayed_frame(h, pict, got_frame, 0);

if (h->is_avc && av_packet_get_side_data(avpkt, AV_PKT_DATA_NEW_EXTRADATA, NULL)) {
int side_size;
uint8_t *side = av_packet_get_side_data(avpkt, AV_PKT_DATA_NEW_EXTRADATA, &side_size);
if (is_extra(side, side_size))
ff_h264_decode_extradata(side, side_size,
&h->ps, &h->is_avc, &h->nal_length_size,
avctx->err_recognition, avctx);
}
if(h->is_avc && buf_size >= 9 && buf[0]==1 && buf[2]==0 && (buf[4]&0xFC)==0xFC && (buf[5]&0x1F) && buf[8]==0x67){
if (is_extra(buf, buf_size))
return ff_h264_decode_extradata(buf, buf_size,
&h->ps, &h->is_avc, &h->nal_length_size,
avctx->err_recognition, avctx);
}

buf_index = decode_nal_units(h, buf, buf_size);
if (buf_index < 0)
return AVERROR_INVALIDDATA;

if (!h->cur_pic_ptr && h->nal_unit_type == H264_NAL_END_SEQUENCE) {
av_assert0(buf_index <= buf_size);
return send_next_delayed_frame(h, pict, got_frame, buf_index);
}

if (!(avctx->flags2 & AV_CODEC_FLAG2_CHUNKS) && (!h->cur_pic_ptr || !h->has_slice)) {
if (avctx->skip_frame >= AVDISCARD_NONREF ||
buf_size >= 4 && !memcmp("Q264", buf, 4))
return buf_size;
av_log(avctx, AV_LOG_ERROR, "no frame!\n");
return AVERROR_INVALIDDATA;
}

if (!(avctx->flags2 & AV_CODEC_FLAG2_CHUNKS) ||
(h->mb_y >= h->mb_height && h->mb_height)) {
if ((ret = ff_h264_field_end(h, &h->slice_ctx[0], 0)) < 0)
return ret;

/* Wait for second field. */
if (h->next_output_pic) {
ret = finalize_frame(h, pict, h->next_output_pic, got_frame);
if (ret < 0)
return ret;
}
}

av_assert0(pict->buf[0] || !*got_frame);

ff_h264_unref_picture(h, &h->last_pic_for_ec);

return get_consumed_bytes(buf_index, buf_size);
}