Re: read beyond buffer

Hello Martin,

any value will do for the padding. The padded area is read but not used by
the decoder.

Regards,
Michael


Quoting Martin Kuball <[email protected]>:

> Thanks for the answer. Now I wonder what values I should use for padding.
> Will zeros do or should I use a pattern like 0 0 1? I'm asking because in
> some places in the xvid code I see calls to method check_resync_marker and
> the rsync marker is 1.
>
> Martin
>
>
> Am Wednesday, 1. November 2006 18:39 schrieb Michael Militzer:
>> Hello Martin,
>>
>> Xvid cvs head and 1.1.2 versions perform a cross check before accessing
>> *(bs->tail+2) if XVID_SAFE_BS_TAIL is defined in bitstream.h. This check
>> however costs performance. Hence, we recommend you should not use the
>> XVID_SAFE_BS_TAIL flag but instead pad your input buffers to 8 bytes if
>> any possible.
>>
>> Regards,
>> Michael
>>
>> Quoting Martin Kuball <[email protected]>:
>> > Hi!
>> >
>> > I'm writing an application that uses libxvid 1.1.0 to decode mpeg4
>> > videos. I noticed that when calling
>> >
>> > 	frameStruct.bitstream = input_buffer;
>> > 	frameStruct.length = length;  //length of input_buffer
>> > 	xvid_decore(handle, XVID_DEC_DECODE, &frameStruct, &statusStruct);
>> >
>> > xvid is sometimes accesing bytes beyond input_buffer[length-1]. This
>> > happens everytime a userdata frame is red and somethimes with vops,
>> > too. I could not find any documentation saying that you need to
>> > provide extra space at the end of the buffer. And actually if you
>> > provide a length field in the API I consider it as a bug if it is not
>> > honoured.
>> >
>> > So what is necessary to make it work reliably?
>> >
>> > By the way I could not check with version 1.1.1 because I was not able
>> > to download it. Seems to be some broken links on the web page.
>> >
>> > Martin
>> > _______________________________________________
>> > XviD-users mailing list
>> > [email protected]
>> > http://list.xvid.org/mailman/listinfo/xvid-users
>>
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