[FFmpeg-devel] camera files (no name)

[nicolas martin]

Le 09-02-06 ? 16:52, Michael Niedermayer a ?crit :

> On Fri, Feb 06, 2009 at 04:26:02PM -0500, nicolas martin wrote:
>>
>> Le 09-02-06 ? 14:06, Michael Niedermayer a ?crit :
>>
>>> On Fri, Feb 06, 2009 at 01:43:27PM -0500, nicolas martin wrote:
>>>>
>>>> Le 09-02-06 ? 12:20, Michael Niedermayer a ?crit :
>>>>
>>>>> On Fri, Feb 06, 2009 at 08:14:30AM -0500, nicolas martin wrote:
>>>>>>
>>>>>>> On Wed, Feb 04, 2009 at 01:23:16PM -0500, nicolas martin wrote:
>>>>>>>>
>>>>>>>>> On Tue, Feb 03, 2009 at 04:27:51PM -0500, nicolas martin  
>>>>>>>>> wrote:
>>>>>>>>>> Attached is a patch to support the nc4600 camera files.
>>>>>>>>>>
>>>>>>>>>> Thanks in advance for reviewing and replying.
>>>>>>>>>
>>>>>>>>> Changelog and docs update is missing.
>>>>>>>>
>>>>>>>> Doc update and changelog since when ?
>>>>>>>
>>>>>>> If you add a new demuxer, you should add an entry for it to the
>>>>>>> changelog and the format support list in doc/general.texi.
>>>>>>>
>>>>>>
>>>>>> In reply to what Peter Ross wrote, I can't find its mail though
>>>>>>
>>>>>>>>> + if (size <= 0) {
>>>>>>>>> + av_log(s, AV_LOG_DEBUG, "Wrong size : %d\n", size);
>>>>>>>> While size may be zero, it will never be less then zero, thus  
>>>>>>>> the
>>>>>>>> debug
>>>>>>>> statement is pointless.
>>>>>> The size can't be less than zero, I changed it.
>>>>>> However if the size is zero, then we have a problem, so the debug
>>>>>> statement
>>>>>> is meaningful.
>>>>>
>>>>> [...]
>>>>>> +static int nc_read_packet(AVFormatContext *s, AVPacket *pkt)
>>>>>> +{
>>>>>> +    int size;
>>>>>> +
>>>>>> +    uint32_t state=-1;
>>>>>> +    while(!url_feof(s->pb) && state != NC_VIDEO_FLAG)
>>>>>> +        state = (state<<8) + get_byte(s->pb);
>>>>>> +
>>>>>> +    get_byte(s->pb);
>>>>>> +    size = get_le16(s->pb);
>>>>>> +    url_fskip(s->pb, 9);
>>>>>> +
>>>>>
>>>>>> +    if (size == 0) {
>>>>>> +        av_log(s, AV_LOG_DEBUG, "Wrong size : %d\n", size);
>>>>>> +        return AVERROR_INVALIDDATA;
>>>>>> +    }
>>>>>
>>>>> what is the problem with not returning an error in this case?
>>>>
>>>> Well I think that the camera is not supposed to send packet with  
>>>> size 0.
>>>> If
>>>> it happens, it probably means the data got corrupted, or an error
>>>> occured.
>>>> In any case, I don't think you can do anything besides returning  
>>>> an error
>>>> ... maybe try to skip data until the next header ??
>>>> As I don't think it is supposed to happen, I choose to treat it  
>>>> like
>>>> this.
>>>> What do you think ??
>>>
>>> id print a warning and continue, the code should be able to find and
>>> continue
>>> at the next valid frame
>>
>> Ok so I changed it so that while (size==0) it loops until it finds  
>> a valid
>> size.
>> Though i think it should never happen, if it happens, better pray  
>> that it's
>> a corrupted data,
>> my guess is that it will loop forever ...
>> Should I add a count to break if it repeateadly gives a null size ?  
>> or is
>> the solution I brought enough ?
>
> it should fail at EOF to prevent an infinite loop
> and it might make sense to retun EAGAIN instead of looping, this also
> might be simpler

What about something like that ?

>
>
> [...]
> -- 
> Michael     GnuPG fingerprint:  
> 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> Why not whip the teacher when the pupil misbehaves? -- Diogenes of  
> Sinope
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