Quoting Vittorio Giovara (2016-06-09 18:08:23)
> On Thu, Jun 9, 2016 at 4:29 AM, Anton Khirnov <an...@khirnov.net> wrote:
> > There is no bitstream parsing in that block and messing with
> > decoder-global state is not something that belongs into header parsing.
> >
> > Nothing else in this function depends on the value of current_slice,
> > except for two validity checks. Those checks are also moved out of
> > slice_header_parse().
> > ---
> > libavcodec/h264_slice.c | 68
> > ++++++++++++++++++++++++-------------------------
> > 1 file changed, 33 insertions(+), 35 deletions(-)
> >
> > diff --git a/libavcodec/h264_slice.c b/libavcodec/h264_slice.c
> > index 17608b4..c43a0be 100644
> > --- a/libavcodec/h264_slice.c
> > +++ b/libavcodec/h264_slice.c
> > @@ -1177,21 +1177,6 @@ static int h264_slice_header_parse(H264Context *h,
> > H264SliceContext *sl,
> >
> > sl->first_mb_addr = get_ue_golomb(&sl->gb);
> >
> > - if (sl->first_mb_addr == 0) { // FIXME better field boundary detection
> > - if (h->current_slice && h->cur_pic_ptr && FIELD_PICTURE(h)) {
> > - ff_h264_field_end(h, sl, 1);
> > - }
> > -
> > - h->current_slice = 0;
> > - if (!h->first_field) {
> > - if (h->cur_pic_ptr && !h->droppable) {
> > - ff_thread_report_progress(&h->cur_pic_ptr->tf, INT_MAX,
> > - h->picture_structure ==
> > PICT_BOTTOM_FIELD);
> > - }
> > - h->cur_pic_ptr = NULL;
> > - }
> > - }
> > -
> > slice_type = get_ue_golomb_31(&sl->gb);
> > if (slice_type > 9) {
> > av_log(h->avctx, AV_LOG_ERROR,
> > @@ -1226,11 +1211,6 @@ static int h264_slice_header_parse(H264Context *h,
> > H264SliceContext *sl,
> > sl->pps_id);
> > return AVERROR_INVALIDDATA;
> > }
> > - if (h->current_slice > 0 &&
> > - h->ps.pps != (const PPS*)h->ps.pps_list[sl->pps_id]->data) {
> > - av_log(h->avctx, AV_LOG_ERROR, "PPS changed between slices\n");
> > - return AVERROR_INVALIDDATA;
> > - }
> > pps = (const PPS*)h->ps.pps_list[sl->pps_id]->data;
> >
> > if (!h->ps.sps_list[pps->sps_id]) {
> > @@ -1265,21 +1245,6 @@ static int h264_slice_header_parse(H264Context *h,
> > H264SliceContext *sl,
> > sl->picture_structure = picture_structure;
> > sl->mb_field_decoding_flag = picture_structure != PICT_FRAME;
> >
> > - if (h->current_slice != 0) {
> > - if (h->picture_structure != picture_structure ||
> > - h->droppable != droppable) {
> > - av_log(h->avctx, AV_LOG_ERROR,
> > - "Changing field mode (%d -> %d) between slices is not
> > allowed\n",
> > - h->picture_structure, picture_structure);
> > - return AVERROR_INVALIDDATA;
> > - } else if (!h->cur_pic_ptr) {
> > - av_log(h->avctx, AV_LOG_ERROR,
> > - "unset cur_pic_ptr on slice %d\n",
> > - h->current_slice + 1);
> > - return AVERROR_INVALIDDATA;
> > - }
> > - }
> > -
> > if (picture_structure == PICT_FRAME) {
> > h->curr_pic_num = h->poc.frame_num;
> > h->max_pic_num = 1 << sps->log2_max_frame_num;
> > @@ -1430,10 +1395,43 @@ int ff_h264_decode_slice_header(H264Context *h,
> > H264SliceContext *sl,
> > if (ret < 0)
> > return ret;
> >
> > + if (sl->first_mb_addr == 0) { // FIXME better field boundary detection
>
> does this FIXME still apply?
Yes, this code is still rather hacky, e.g. it will break on slice
threading.
--
Anton Khirnov
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