[FFmpeg-devel] camera files (no name)

[nicolas martin]

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 ?

>
>
> [...]
> -- 
> Michael     GnuPG fingerprint:  
> 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> Complexity theory is the science of finding the exact solution to an
> approximation. Benchmarking OTOH is finding an approximation of the  
> exact
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