[FFmpeg-devel] [PATCH] get/show_bits() can read up to MIN_CACHE_BITS bits

[Stefan Gehrer]

M?ns Rullg?rd wrote:
> Stefan Gehrer <stefan.gehrer at gmx.de> writes:
> 
>> Mans Rullgard wrote:
>>> The limit for get/show_bits_long() to use get/show_bits() directly
>>> should be MIN_CACHE_BITS, not 17.
>> I think something like attached should go with it.
>> Index: libavcodec/get_bits.h
>> ===================================================================
>> --- libavcodec/get_bits.h	(revision 21936)
>> +++ libavcodec/get_bits.h	(working copy)
>> @@ -356,7 +356,7 @@
>>  }
>>  
>>  /**
>> - * reads 1-17 bits.
>> + * reads between 1 and MIN_CACHE_BITS bits.
>>   * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
>>   */
>>  static inline unsigned int get_bits(GetBitContext *s, int n){
>> @@ -370,7 +370,7 @@
>>  }
>>  
>>  /**
>> - * shows 1-17 bits.
>> + * shows between 1 and MIN_CACHE_BITS bits.
>>   * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
>>   */
>>  static inline unsigned int show_bits(GetBitContext *s, int n){
> 
> I disagree.  17 is the maximum number of bits guaranteed to be
> readable with any choice of implementation.  If you want to improve
> the documentation, you should explain how MIN_CACHE_BITS is assigned
> somewhere.  You should also make it clear that a specific reader
> should be forced only in special cases.

So people that use an alternative bitstream reader should still call
the functions with n<=17 in order to keep the readers interchangeable.
Makes sense.
Since I don't know when it is indicated to use another than the
default reader, I can't improve the documentation much, so just
forget the patch.

Stefan