[FFmpeg-devel] [PATCH] avcodec/h264_ps: fix storage size for offset_for_ref_frame

James Almer jamrial at gmail.com
Thu Apr 25 00:37:55 EEST 2019


On 4/16/2019 6:48 PM, Mark Thompson wrote:
> On 11/04/2019 04:10, James Almer wrote:
>> On 4/10/2019 3:30 PM, James Almer wrote:
>>> The spec defines the valid range of values to be INT32_MIN + 1 to INT32_MAX, inclusive.
>>>
>>> Signed-off-by: James Almer <jamrial at gmail.com>
>>> ---
>>> A good example of why making offsets and sizes of structs like this tied to the
>>> ABI is not a good idea.
>>>
>>>  libavcodec/h264_ps.h | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/libavcodec/h264_ps.h b/libavcodec/h264_ps.h
>>> index e967b9cbcf..9014326dfb 100644
>>> --- a/libavcodec/h264_ps.h
>>> +++ b/libavcodec/h264_ps.h
>>> @@ -81,7 +81,7 @@ typedef struct SPS {
>>>      uint32_t num_units_in_tick;
>>>      uint32_t time_scale;
>>>      int fixed_frame_rate_flag;
>>> -    short offset_for_ref_frame[256]; // FIXME dyn aloc?
>>> +    int32_t offset_for_ref_frame[256];
>>
>> The doxy for get_se_golomb() doesn't mention the range of values it can
>> handle, but seeing there's also a get_se_golomb_long(), I guess the
>> relevant line in h264_ps.c should now use the latter instead?
> 
> I think it's correct to do that.  Seems highly unlikely anyone would ever hit it outside a conformance-checking context, though - using anything other than pic_order_cnt_type 0 for nontrivial reference structures is madness.
> 
>>>      int bitstream_restriction_flag;
>>>      int num_reorder_frames;
>>>      int scaling_matrix_present;
> 
> There are some other fields with int32_t range which are using get_se_golomb() - e.g. offset_for_non_ref_pic.  I guess they should use get_se_golomb_long() as above.  They're also plain ints - do they want to be explicitly int32_t?

Pushed this patch, and another making offset_for_ref_frame,
offset_for_non_ref_pic, and offset_for_top_to_bottom_field use
get_se_golomb_long().

Thanks.


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