2018-01-20 3:14 GMT+01:00 Michael Niedermayer <mich...@niedermayer.cc>: > On Sat, Jan 20, 2018 at 02:36:08AM +0100, Carl Eugen Hoyos wrote: >> 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? > > yes
Pushed with this new value. Thank you, Carl Eugen _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
