On 2/26/2016 2:44 PM, Carl Eugen Hoyos wrote: > Derek Buitenhuis <derek.buitenhuis <at> gmail.com> writes: > >> On 2/25/2016 4:30 PM, Carl Eugen Hoyos wrote: > You misunderstand: > Most "imageauto" demuxers return a score of 51. In all cases > when 51 is returned, the detection is nearly certain. Your > patch disables the detection for all these cases (although > it is nearly certain) in favour of the mime type. > > (That is how I understand the patch, please correct me if > setting mime_type actually has another effect than > returning 75 in case of conformance.) > > I don't think the solution is to increase the score for > these probe functions: mpeg streams may start with any > bytes and 32 bit accordance should not return maximum > (or nearly maximum) score.
See below. The scoring should be fixed. > My argument is: Let's please improve the jpeg auto-detection > (the only one that shows issues) instead of disabling it. Forgot what this particular patch does for a second. I'm not saying it should be disabled. I'm saying scoring should be as such: 1) Probing the file file itself: Highest score. 2) Mime-type: Medium score. 3) File extension: Lower score. Mime-type is a *much* better mechanism for detection than file extension over HTTP(S), and it will not affect detection in local files at all. Mime-type should be tried before e.g. mp3 probing, which seems to have a lot of misdirections. This can only be a net improvement, IMO. > (You should be slightly more careful with your arguments: > I originally thought that there might be one or two probe > functions that should sometimes return a score instead of > 0 because the decoders may accept invalid files but that > is not the case except for the case without mime_type.) > > There are 14 "imageauto" demuxers with image type > auto-detection. Three (png, dds, webp) return a score of 99, > I don't know if they would be effected by the patch in > question or not but all three decoders do not work if the > respective probe function fails. > > The qdraw decoder fails for samples that fail auto-detection. > > Of the nine image format types with probe functions that > return 51, the following fail decoding if the probe > function returns 0: > bmp, dpx, exr, j2k, sgi, sunrast, tiff > > The pictor decoder fails for images that are not > auto-detected. > > That leaves only the jpegls autodetection that may not > return a score for images that can be decoded: Since the > patch you provided does not add a mime_type for jpegls, > I don't think it can be used as an argument here. > > So let's improve the jpeg auto-detection, I know it isn't > perfect yet. See above. It's not meant to replace, it's meant to augment. > I am sorry if I misunderstand this (who does "the push"?): > Are you arguing user-set mime_types are (except for jpeg) > more plausible than an autodetection that never returns 0 > for images that can be decoded? Again, see above where I have laid out the scoring I think would be appropriate. However, mime-type is far, far more likely to be accurate than the file extension. I am arguing that it's better than that, for URLs. - Derek _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
