[FFmpeg-devel] [PATCH]lavf/cafdec: Do not fail hard for files ending with junk

[Carl Eugen Hoyos]

2019-01-22 12:04 GMT+01:00, Paul B Mahol <onemda at gmail.com>:
> On 1/22/19, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>> 2019-01-22 11:56 GMT+01:00, Paul B Mahol <onemda at gmail.com>:
>>> On 1/22/19, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>>>> 2019-01-22 11:38 GMT+01:00, Paul B Mahol <onemda at gmail.com>:
>>>>> On 1/22/19, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>>>>>> 2019-01-22 11:28 GMT+01:00, Paul B Mahol <onemda at gmail.com>:
>>>>>>> On 1/22/19, Paul B Mahol <onemda at gmail.com> wrote:
>>>>>>>> On 1/22/19, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>>>>>>>>> 2019-01-15 13:17 GMT+01:00, Paul B Mahol <onemda at gmail.com>:
>>>>>>>>>> On 1/15/19, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>>>>>>>>>>> 2019-01-15 12:53 GMT+01:00, Paul B Mahol <onemda at gmail.com>:
>>>>>>>>>>>> On 1/15/19, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>>>>>>>>>>>>> 2019-01-15 10:23 GMT+01:00, Paul B Mahol <onemda at gmail.com>:
>>>>>>>>>>>>>> On 1/15/19, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>>> A user provided a real-life caf file ending with junk after
>>>>>>>>>>>>>>> the
>>>>>>>>>>>>>>> data
>>>>>>>>>>>>>>> chunk, QuickTime reads such files.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Please comment, Carl Eugen
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> NACK, there is data after junk bytes, which would get simply
>>>>>>>>>>>>>> discarded with your patch.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Please elaborate: I don't think any data gets discarded because
>>>>>>>>>>>>> of this patch.
>>>>>>>>>>>>
>>>>>>>>>>>> I told you already, hex edit size of data chunk to very big
>>>>>>>>>>>> number
>>>>>>>>>>>> and
>>>>>>>>>>>> play file again.
>>>>>>>>>>>
>>>>>>>>>>> Of course.
>>>>>>>>>>>
>>>>>>>>>>> But how does this change the output compared to my patch?
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> It does change, full length of audio is:
>>>>>>>>>>
>>>>>>>>>> MD5=5128bc2cd0e7b0560f15dd4c0546d1a0rate=   0.0kbits/s speed= 777x
>>>>>>>>>> size=       0kB time=00:09:18.16 bitrate=   0.0kbits/s speed= 769x
>>>>>>>>>
>>>>>>>>> Sorry for the delay:
>>>>>>>>> QuickTime Player only plays the file for ~6:20.
>>>>>>>>> Playing the file longer would be an issue since atoms after the
>>>>>>>>> data atom are allowed.
>>>>>>>>> And most important: This is unrelated, my patch is about playing
>>>>>>>>> a file that is supposed to be played but currently doesn't work.
>>>>>>>>> If there is something else to be improved, it should be a separate
>>>>>>>>> patch.
>>>>>>>>>
>>>>>>>>> Please comment, Carl Eugen
>>>>>>>>
>>>>>>>> You can not claim it fixes playback.
>>>>>>
>>>>>> It does here: The file does not play without my patch, it plays
>>>>>> (for the right duration) with my patch.
>>>>>
>>>>> Duration is not right at all.
>>>>
>>>> Does QuickTime play the file longer for you than FFmpeg
>>>> with my patch?
>>>> Or do I misunderstand you?
>>>
>>> Correct duration is one I showed it here.
>>
>> No, the correct duration for the given file is ~6:20 as
>> already explained.
>
> Nope, you are removing actual valid audio samples this way.

But the caf structure claims that the discussed data are
not valid audio samples but other caf atoms, since valid
files exist that have atoms there, it is correct to skip the
atoms if they cannot be detected, that is just how caf
works.
Is my explanation sufficient for you now?

Carl Eugen