h264: drop any pretense of support for data partitioning

It does not work correctly and apparently never did. There is no
indication that this (mis)feature is ever used in the wild or even that
any software other than the reference supports it.

Since the code that attempts to support it adds some nontrivial
complexity and has resulted in several bugs in the past, it is better to
just drop it.

libavcodec/h264.c

@@ -1499,7 +1499,6 @@ again:
                 init_get_bits(&hx->gb, ptr, bit_length);
                 hx->intra_gb_ptr      =
                 hx->inter_gb_ptr      = &hx->gb;
-                hx->data_partitioning = 0;
 
                 if ((err = ff_h264_decode_slice_header(hx, h)))
                     break;
@@ -1552,46 +1551,11 @@ again:
                 }
                 break;
             case NAL_DPA:
-                if (h->avctx->flags & CODEC_FLAG2_CHUNKS) {
-                    av_log(h->avctx, AV_LOG_ERROR,
-                           "Decoding in chunks is not supported for "
-                           "partitioned slices.\n");
-                    return AVERROR(ENOSYS);
-                }
-
-                init_get_bits(&hx->gb, ptr, bit_length);
-                hx->intra_gb_ptr =
-                hx->inter_gb_ptr = NULL;
-
-                if ((err = ff_h264_decode_slice_header(hx, h)) < 0) {
-                    /* make sure data_partitioning is cleared if it was set
-                     * before, so we don't try decoding a slice without a valid
-                     * slice header later */
-                    h->data_partitioning = 0;
-                    break;
-                }
-
-                hx->data_partitioning = 1;
-                break;
             case NAL_DPB:
-                init_get_bits(&hx->intra_gb, ptr, bit_length);
-                hx->intra_gb_ptr = &hx->intra_gb;
-                break;
             case NAL_DPC:
-                init_get_bits(&hx->inter_gb, ptr, bit_length);
-                hx->inter_gb_ptr = &hx->inter_gb;
-
-                if (hx->redundant_pic_count == 0 &&
-                    hx->intra_gb_ptr &&
-                    hx->data_partitioning &&
-                    h->cur_pic_ptr && h->context_initialized &&
-                    (avctx->skip_frame < AVDISCARD_NONREF || hx->nal_ref_idc) &&
-                    (avctx->skip_frame < AVDISCARD_BIDIR  ||
-                     hx->slice_type_nos != AV_PICTURE_TYPE_B) &&
-                    (avctx->skip_frame < AVDISCARD_NONKEY ||
-                     hx->slice_type_nos == AV_PICTURE_TYPE_I) &&
-                    avctx->skip_frame < AVDISCARD_ALL)
-                    context_count++;
+                avpriv_request_sample(avctx, "data partitioning");
+                ret = AVERROR(ENOSYS);
+                goto end;
                 break;
             case NAL_SEI:
                 init_get_bits(&h->gb, ptr, bit_length);
@@ -1718,9 +1682,6 @@ static int h264_decode_frame(AVCodecContext *avctx, void *data,
     int ret;
 
     h->flags = avctx->flags;
-    /* reset data partitioning here, to ensure GetBitContexts from previous
-     * packets do not get used. */
-    h->data_partitioning = 0;
 
     /* end of stream, output what is still in the buffers */
 out:

libavcodec/h264.h

@@ -324,7 +324,6 @@ typedef struct H264Context {
 
     int qscale;
     int droppable;
-    int data_partitioning;
     int coded_picture_number;
     int low_delay;
 

libavcodec/h264_slice.c

@@ -1127,7 +1127,6 @@ static int h264_slice_header_init(H264Context *h, int reinit)
             c->chroma_y_shift    = h->chroma_y_shift;
             c->qscale            = h->qscale;
             c->droppable         = h->droppable;
-            c->data_partitioning = h->data_partitioning;
             c->low_delay         = h->low_delay;
             c->mb_width          = h->mb_width;
             c->mb_height         = h->mb_height;