[FFmpeg-devel] [PATCH] cbs_vp9: Ensure that reserved zero bits are actually zero

[Mark Thompson]

---
On 27/10/18 20:26, James Almer wrote:
> On 10/27/2018 4:13 PM, James Almer wrote:
>> On 10/27/2018 4:11 PM, Mark Thompson wrote:
>>> On 26/10/18 20:37, James Almer wrote:
>>>> Signed-off-by: James Almer <jamrial at gmail.com>
>>>> ---
>>>>  libavcodec/cbs_vp9_syntax_template.c | 1 +
>>>>  1 file changed, 1 insertion(+)
>>>>
>>>> diff --git a/libavcodec/cbs_vp9_syntax_template.c b/libavcodec/cbs_vp9_syntax_template.c
>>>> index 0db0f52a6d..b4a7f65e85 100644
>>>> --- a/libavcodec/cbs_vp9_syntax_template.c
>>>> +++ b/libavcodec/cbs_vp9_syntax_template.c
>>>> @@ -65,6 +65,7 @@ static int FUNC(color_config)(CodedBitstreamContext *ctx, RWContext *rw,
>>>>          if (profile == 1 || profile == 3) {
>>>>              infer(subsampling_x, 0);
>>>>              infer(subsampling_y, 0);
>>>> +            f(1, color_config_reserved_zero);
>>>>          }
>>>>      }
>>>>  
>>>>
>>>
>>> This and the one above should probably be called "reserved_zero" for trace purposes.  Not sure where the longer name came from.
>>>
>>
>> Yeah, the spec simply says reserved_zero, so i'll change it.
> 
> Looks like you came up with the longer name because there's another
> "reserved_zero" field in the uncompressed header, and of course you
> couldn't use it for both.
> 
> The solution would be to move the color config fields to its own struct
> called VP9RawColorConfig, like you did in cbs av1.

Or this, so we don't store them at all :)


 libavcodec/cbs_vp9.c                 | 13 +++++++++++++
 libavcodec/cbs_vp9.h                 |  2 --
 libavcodec/cbs_vp9_syntax_template.c |  6 +++---
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/libavcodec/cbs_vp9.c b/libavcodec/cbs_vp9.c
index 7498be4b73..c03ce986c0 100644
--- a/libavcodec/cbs_vp9.c
+++ b/libavcodec/cbs_vp9.c
@@ -314,6 +314,12 @@ static int cbs_vp9_write_le(CodedBitstreamContext *ctx, PutBitContext *pbc,
         current->name = prob; \
     } while (0)
 
+#define fixed(width, name, value) do { \
+        av_unused uint32_t fixed_value = value; \
+        CHECK(ff_cbs_read_unsigned(ctx, rw, width, #name, \
+                                   0, &fixed_value, value, value)); \
+    } while (0)
+
 #define infer(name, value) do { \
         current->name = value; \
     } while (0)
@@ -331,6 +337,7 @@ static int cbs_vp9_write_le(CodedBitstreamContext *ctx, PutBitContext *pbc,
 #undef fle
 #undef delta_q
 #undef prob
+#undef fixed
 #undef infer
 #undef byte_alignment
 
@@ -370,6 +377,11 @@ static int cbs_vp9_write_le(CodedBitstreamContext *ctx, PutBitContext *pbc,
             xf(8, name.prob, current->name, subs, __VA_ARGS__); \
     } while (0)
 
+#define fixed(width, name, value) do { \
+        CHECK(ff_cbs_write_unsigned(ctx, rw, width, #name, \
+                                    0, value, value, value)); \
+    } while (0)
+
 #define infer(name, value) do { \
         if (current->name != (value)) { \
             av_log(ctx->log_ctx, AV_LOG_WARNING, "Warning: " \
@@ -392,6 +404,7 @@ static int cbs_vp9_write_le(CodedBitstreamContext *ctx, PutBitContext *pbc,
 #undef fle
 #undef delta_q
 #undef prob
+#undef fixed
 #undef infer
 #undef byte_alignment
 
diff --git a/libavcodec/cbs_vp9.h b/libavcodec/cbs_vp9.h
index 7eee6d5e9e..ac66da5af1 100644
--- a/libavcodec/cbs_vp9.h
+++ b/libavcodec/cbs_vp9.h
@@ -84,7 +84,6 @@ typedef struct VP9RawFrameHeader {
     uint8_t frame_marker;
     uint8_t profile_low_bit;
     uint8_t profile_high_bit;
-    uint8_t profile_reserved_zero;
 
     uint8_t show_existing_frame;
     uint8_t frame_to_show_map_idx;
@@ -99,7 +98,6 @@ typedef struct VP9RawFrameHeader {
     uint8_t color_range;
     uint8_t subsampling_x;
     uint8_t subsampling_y;
-    uint8_t color_config_reserved_zero;
 
     uint8_t refresh_frame_flags;
 
diff --git a/libavcodec/cbs_vp9_syntax_template.c b/libavcodec/cbs_vp9_syntax_template.c
index cd5b83a4f5..ec8463e6d7 100644
--- a/libavcodec/cbs_vp9_syntax_template.c
+++ b/libavcodec/cbs_vp9_syntax_template.c
@@ -59,7 +59,7 @@ static int FUNC(color_config)(CodedBitstreamContext *ctx, RWContext *rw,
         if (profile == 1 || profile == 3) {
             f(1, subsampling_x);
             f(1, subsampling_y);
-            f(1, color_config_reserved_zero);
+            fixed(1, reserved_zero, 0);
         } else {
             infer(subsampling_x, 1);
             infer(subsampling_y, 1);
@@ -69,7 +69,7 @@ static int FUNC(color_config)(CodedBitstreamContext *ctx, RWContext *rw,
         if (profile == 1 || profile == 3) {
             infer(subsampling_x, 0);
             infer(subsampling_y, 0);
-            f(1, color_config_reserved_zero);
+            fixed(1, reserved_zero, 0);
         }
     }
 
@@ -278,7 +278,7 @@ static int FUNC(uncompressed_header)(CodedBitstreamContext *ctx, RWContext *rw,
     f(1, profile_high_bit);
     profile = (current->profile_high_bit << 1) + current->profile_low_bit;
     if (profile == 3)
-        f(1, profile_reserved_zero);
+        fixed(1, reserved_zero, 0);
 
     f(1, show_existing_frame);
     if (current->show_existing_frame) {
-- 
2.19.1