2018-01-19 23:42 GMT+01:00 Michael Niedermayer <mich...@niedermayer.cc>: > On Fri, Jan 19, 2018 at 07:25:43PM +0100, Carl Eugen Hoyos wrote: >> 2018-01-19 18:51 GMT+01:00 Michael Niedermayer <mich...@niedermayer.cc>: >> > On Thu, Jan 18, 2018 at 09:28:40PM +0100, Carl Eugen Hoyos wrote: >> >> Hi! >> >> >> >> The probe score for swf files (with uncompressed headers) is currently >> >> very high after testing a little more than 24bit, attached patch >> >> reduces the score. >> > >> > hmm >> > the first 24 bits are tested and all but 2 values are rejected >> > >> > thats 23 bits that must match >> >> Ok. >> >> > then 4 values are tested which can be from 1 to 31 bits each >> > the tests are each either == 0 or != 0 so they are a bit weak >> > but its at least adding 4 bits that must match and also len >> >> I was sure this is not equivalent to four bits on a specific >> position (but for the patch I assumed a "best case scenario" >> where this actually were the case). >> >> > itself has to be smallish so we could argue that this gets us to >> > about 28 bits >> >> > and then buf[3] is checked to be < 20 >> > at this point we need about 32bits to be matching, still not huge but >> > id think this is stronger than what file extensions prove which are >> > MAX/2 >> >> We return MAX/2 for many "initial 32 bits" tests and I believe >> we made good experience (and for MAX/2 the extension is >> ignored or do I misremember?) >> > >> > The test is weakened by using 0 / not 0 / ascii as values though >> > >> > Have you seen an actual probe failure ? >> >> No, I was looking at another issue. > > we have many files with wrong extensions, its not uncommon
Yes, I misremembered how extensions are rated, I actually wanted to set the return value to "AVPROBE_SCORE_EXTENSION + 1". Would that be ok? Carl Eugen _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
