Re: [libav-devel] [PATCH 08/11] cbs_mpeg2: Add support for picture display extension

[Luca Barbato]

On 10/09/2017 01:09, Mark Thompson wrote:

---
Many of the conformance test files have it.


  libavcodec/cbs_mpeg2.h                 |  8 +++++++
  libavcodec/cbs_mpeg2_syntax_template.c | 44 ++++++++++++++++++++++++++++++++++
  2 files changed, 52 insertions(+)

diff --git a/libavcodec/cbs_mpeg2.h b/libavcodec/cbs_mpeg2.h
index 32c4d4e2b..0b6cb998d 100644
--- a/libavcodec/cbs_mpeg2.h
+++ b/libavcodec/cbs_mpeg2.h
@@ -160,6 +160,11 @@ typedef struct MPEG2RawQuantMatrixExtension {
      uint8_t chroma_non_intra_quantiser_matrix[64];
  } MPEG2RawQuantMatrixExtension;

+typedef struct MPEG2RawPictureDisplayExtension {

+    uint16_t frame_centre_horizontal_offset[3];
+    uint16_t frame_centre_vertical_offset[3];
+} MPEG2RawPictureDisplayExtension;
+
  typedef struct MPEG2RawExtensionData {
      uint8_t extension_start_code;
      uint8_t extension_start_code_identifier;
@@ -169,6 +174,7 @@ typedef struct MPEG2RawExtensionData {
          MPEG2RawSequenceDisplayExtension sequence_display;
          MPEG2RawQuantMatrixExtension quant_matrix;
          MPEG2RawPictureCodingExtension picture_coding;
+        MPEG2RawPictureDisplayExtension picture_display;
      } data;
  } MPEG2RawExtensionData;

@@ -206,6 +212,8 @@ typedef struct CodedBitstreamMPEG2Context {

      uint16_t vertical_size;
      uint8_t scalable;
      uint8_t scalable_mode;
+    uint8_t progressive_sequence;
+    uint8_t number_of_frame_centre_offsets;

// Write buffer.

      uint8_t *write_buffer;
diff --git a/libavcodec/cbs_mpeg2_syntax_template.c 
b/libavcodec/cbs_mpeg2_syntax_template.c
index b6dd42d2e..4aa1eb3c0 100644
--- a/libavcodec/cbs_mpeg2_syntax_template.c
+++ b/libavcodec/cbs_mpeg2_syntax_template.c
@@ -101,6 +101,7 @@ static int FUNC(sequence_extension)(CodedBitstreamContext 
*ctx, RWContext *rw,
          current->horizontal_size_extension << 12;
      mpeg2->vertical_size = (mpeg2->vertical_size & 0xfff) |
          current->vertical_size_extension << 12;
+    mpeg2->progressive_sequence = current->progressive_sequence;

ui(12, bit_rate_extension);

      marker_bit();
@@ -183,6 +184,7 @@ static int FUNC(picture_header)(CodedBitstreamContext *ctx, 
RWContext *rw,
  static int FUNC(picture_coding_extension)(CodedBitstreamContext *ctx, 
RWContext *rw,
                                            MPEG2RawPictureCodingExtension 
*current)
  {
+    CodedBitstreamMPEG2Context *mpeg2 = ctx->priv_data;
      int err;

HEADER("Picture Coding Extension");

@@ -204,6 +206,27 @@ static int 
FUNC(picture_coding_extension)(CodedBitstreamContext *ctx, RWContext
      ui(1, chroma_420_type);
      ui(1, progressive_frame);

+ if (mpeg2->progressive_sequence) {

+        if (current->repeat_first_field) {
+            if (current->top_field_first)
+                mpeg2->number_of_frame_centre_offsets = 3;
+            else
+                mpeg2->number_of_frame_centre_offsets = 2;
+        } else {
+            mpeg2->number_of_frame_centre_offsets = 1;
+        }
+    } else {
+        if (current->picture_structure == 1 || // Top field.
+            current->picture_structure == 2) { // Bottom field.
+            mpeg2->number_of_frame_centre_offsets = 1;
+        } else {
+            if (current->repeat_first_field)
+                mpeg2->number_of_frame_centre_offsets = 3;
+            else
+                mpeg2->number_of_frame_centre_offsets = 2;
+        }
+    }
+
      ui(1, composite_display_flag);
      if (current->composite_display_flag) {
          ui(1, v_axis);
@@ -250,6 +273,24 @@ static int 
FUNC(quant_matrix_extension)(CodedBitstreamContext *ctx, RWContext *r
      return 0;
  }

+static int FUNC(picture_display_extension)(CodedBitstreamContext *ctx, RWContext *rw,

+                                           MPEG2RawPictureDisplayExtension 
*current)
+{
+    CodedBitstreamMPEG2Context *mpeg2 = ctx->priv_data;
+    int err, i;
+
+    HEADER("Picture Display Extension");
+
+    for (i = 0; i < mpeg2->number_of_frame_centre_offsets; i++) {
+        ui(16, frame_centre_horizontal_offset[i]);
+        marker_bit();
+        ui(16, frame_centre_vertical_offset[i]);
+        marker_bit();
+    }
+
+    return 0;
+}
+
  static int FUNC(extension_data)(CodedBitstreamContext *ctx, RWContext *rw,
                                  MPEG2RawExtensionData *current)
  {
@@ -270,6 +311,9 @@ static int FUNC(extension_data)(CodedBitstreamContext *ctx, 
RWContext *rw,
      case 3:
          return FUNC(quant_matrix_extension)
              (ctx, rw, &current->data.quant_matrix);
+    case 7:
+        return FUNC(picture_display_extension)
+            (ctx, rw, &current->data.picture_display);
      case 8:
          return FUNC(picture_coding_extension)
              (ctx, rw, &current->data.picture_coding);

Looks fine.
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