22/1/20 9:52 am, Carl Eugen Hoyos пишет:
>
> Am Mi., 22. Jan. 2020 um 00:33 Uhr schrieb Zane van Iperen
> <z...@zanevaniperen.com>:
>>
>> 21/1/20 11:14 pm, Carl Eugen Hoyos пишет:
>>>
>>> Am Di., 21. Jan. 2020 um 11:09 Uhr schrieb Zane van Iperen
>>> <z...@zanevaniperen.com>:
>>>
>>>> +static int argo_asf_probe(const AVProbeData *p)
>>>> +{
>>>> + int score;
>>>> + ArgoASFFileHeader hdr;
>>>> +
>>>> + av_assert0(AVPROBE_PADDING_SIZE >= ASF_FILE_HEADER_SIZE);
>>>> +
>>>> + argo_asf_parse_file_header(&hdr, p->buf);
>>>> +
>>>> + if (hdr.magic != ASF_TAG)
>>>> + return 0;
>>>
>>>> + /* If this is huge, then it's very likely not an ASF file. */
>>>> + if (hdr.chunk_offset > INT_MAX)
>>>> + return 1;
>>>
>>> Am I correct that this tests only one bit?
>>> This makes sense for many probe functions that can easily
>>> return false positives based on weak heuristics, probe
>>> functions typically return high scores for matching first 32
>>> bits though.
>>
>> I can just get rid of that check completely if it's easier.
>
> Please.
>
Done.
>>>> + score = 0;
>>>> + if (argo_asf_is_known_version(&hdr))
>>>> + score += (AVPROBE_SCORE_MAX / 2) + 1;
>>>
>>> Unusual code style.
>>>
>>>> + /* Have only ever seen these with 1 chunk. */
>>>> + if (hdr.num_chunks == 1)
>>>> + score += 10;
>>>
>>> Returns 0 for argo files with unknown version and more than
>>> one chunk and 10 for for unknown version and one chunk.
>>>
>>> Should be ~25 in both cases, feel free to return a higher
>>> score if all tests pass, I just wanted to simplify the probe
>>> function as testing 32 bit is what is usually done.
>>>
>>
>> Returning 0 on a unknown version is a bug, I want it to hit the
>> avpriv_request_sample() below.
>>
>> Would something like this (untested) be better?
>>
>> > if (hdr.chunk_offset & 0xFF000000U)
>> > return 1;
>> >
>> > score = (AVPROBE_SCORE_MAX / 2) + 1;
>> >
>> > if (!argo_asf_is_known_version(&hdr))
>> > score -= 25;
>> >
>> > /* Have only ever seen these with 1 chunk. */
>> > if (hdr.num_chunks > 1)
>> > score -= 25;
>> >
>> > return score;
>>
>> That way if it fails one check it'll be 26, or 1 if it fails both.
>
> But it should return ~25 if the first 32bit match (but the version
> is wrong) and fail later.
>
> I mostly wanted to argue for a less complicated probe function
> for a format that starts with 32 known bits.
>
Ah, sorry I misunderstood. How's this?
> if (hdr.magic != ASF_TAG)
> return 0;
>
> if (!argo_asf_is_known_version(&hdr))
> return 25;
>
> return (AVPROBE_SCORE_MAX / 2) + 1;
> Carl Eugen
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Zane
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