mirror of https://git.ffmpeg.org/ffmpeg.git
avcodec/mpeg12dec: Allocate dummy frames for non-I fields
MPEG-2 allows to pair an intra field (as first field) together with a P-field. In this case a conformant bitstream has to satisfy certain restrictions in order to ensure that only the I field is used for prediction. See section 7.6.3.5 of the MPEG-2 specifications. We do not check these restrictions; normally we simply allocate dummy frames for reference in order to avoid checks lateron. This happens in ff_mpv_frame_start() and therefore does not happen for a second field. This is inconsistent. Fix this by allocating these dummy frames for the second field, too. This already fixes two bugs: 1. Undefined pointer arithmetic in prefetch_motion() in mpegvideo_motion.c where it is simply presumed that the reference frame exists. 2. Several MPEG-2 hardware accelerations rely on last_picture being allocated for P pictures and next picture for B pictures; e.g. VDPAU returns VDP_STATUS_INVALID_HANDLE when decoding an I-P fields pair because the forward_reference was set incorrectly. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
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@ -1372,6 +1372,9 @@ static int mpeg_field_start(MpegEncContext *s, const uint8_t *buf, int buf_size)
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return ret;
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}
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}
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ret = ff_mpv_alloc_dummy_frames(s);
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if (ret < 0)
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return ret;
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for (int i = 0; i < 3; i++) {
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s->current_picture.f->data[i] = s->current_picture_ptr->f->data[i];
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@ -1727,7 +1730,7 @@ static int slice_decode_thread(AVCodecContext *c, void *arg)
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* Handle slice ends.
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* @return 1 if it seems to be the last slice
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*/
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static int slice_end(AVCodecContext *avctx, AVFrame *pict)
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static int slice_end(AVCodecContext *avctx, AVFrame *pict, int *got_output)
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{
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Mpeg1Context *s1 = avctx->priv_data;
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MpegEncContext *s = &s1->mpeg_enc_ctx;
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@ -1758,14 +1761,16 @@ static int slice_end(AVCodecContext *avctx, AVFrame *pict)
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return ret;
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ff_print_debug_info(s, s->current_picture_ptr, pict);
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ff_mpv_export_qp_table(s, pict, s->current_picture_ptr, FF_MPV_QSCALE_TYPE_MPEG2);
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*got_output = 1;
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} else {
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/* latency of 1 frame for I- and P-frames */
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if (s->last_picture_ptr) {
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if (s->last_picture_ptr && !s->last_picture_ptr->dummy) {
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int ret = av_frame_ref(pict, s->last_picture_ptr->f);
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if (ret < 0)
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return ret;
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ff_print_debug_info(s, s->last_picture_ptr, pict);
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ff_mpv_export_qp_table(s, pict, s->last_picture_ptr, FF_MPV_QSCALE_TYPE_MPEG2);
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*got_output = 1;
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}
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}
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@ -2204,14 +2209,9 @@ static int decode_chunks(AVCodecContext *avctx, AVFrame *picture,
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s2->er.error_count += s2->thread_context[i]->er.error_count;
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}
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ret = slice_end(avctx, picture);
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ret = slice_end(avctx, picture, got_output);
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if (ret < 0)
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return ret;
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else if (ret) {
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// FIXME: merge with the stuff in mpeg_decode_slice
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if (s2->last_picture_ptr || s2->low_delay || s2->pict_type == AV_PICTURE_TYPE_B)
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*got_output = 1;
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}
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}
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s2->pict_type = 0;
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