[FFmpeg-devel] [PATCH] avutil/crc: avoid needless space wastage of hardcoded crc table

James Almer jamrial at gmail.com
Mon Nov 30 03:55:01 CET 2015


On 11/29/2015 11:50 PM, Ganesh Ajjanagadde wrote:
> On Sun, Nov 29, 2015 at 9:45 PM, Ronald S. Bultje <rsbultje at gmail.com> wrote:
>> Hi,
>>
>> On Sun, Nov 29, 2015 at 9:41 PM, Ganesh Ajjanagadde <gajjanagadde at gmail.com>
>> wrote:
>>>
>>> There was no reason AFAIK for making AV_CRC_24_IEEE 12. This simply
>>> resulted in wasted space under --enable-hardcoded-tables:
>>> dynamic: 1318672 libavutil/libavutil.so.55
>>> old    : 1330680 libavutil/libavutil.so.55
>>> new    : 1326488 libavutil/libavutil.so.55
>>>
>>> Minor version number is bumped.
>>>
>>> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde at gmail.com>
>>> ---
>>>  libavutil/crc.h     | 2 +-
>>>  libavutil/version.h | 2 +-
>>>  2 files changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/libavutil/crc.h b/libavutil/crc.h
>>> index e86bf1d..61592df 100644
>>> --- a/libavutil/crc.h
>>> +++ b/libavutil/crc.h
>>> @@ -40,7 +40,7 @@ typedef enum {
>>>      AV_CRC_32_IEEE,
>>>      AV_CRC_32_IEEE_LE,  /*< reversed bitorder version of AV_CRC_32_IEEE
>>> */
>>>      AV_CRC_16_ANSI_LE,  /*< reversed bitorder version of AV_CRC_16_ANSI
>>> */
>>> -    AV_CRC_24_IEEE = 12,
>>> +    AV_CRC_24_IEEE,
>>>      AV_CRC_MAX,         /*< Not part of public API! Do not use outside
>>> libavutil. */
>>>  }AVCRCId;
>>
>>
>> I support the idea, but this breaks ABI. You need to do this under a version
>> bump, see libavutil/version.h for templates.
> 
> Sorry, can you be a little more explicit: I bump the minor version
> number here of avutil. Do you mean to use AV_VERSION_INT and friends
> to check and accordingly place ifdefy?

Changing an enum value in a public header breaks ABI. Software already compiled
that links to libavutil.so.55 expects AV_CRC_24_IEEE to be 12, not 6 as it would
be after this commit.

> 
>>
>> Ronald
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> 



More information about the ffmpeg-devel mailing list