[FFmpeg-devel] camera files (no name)

[Michael Niedermayer]

On Fri, Feb 06, 2009 at 05:15:26PM -0500, nicolas martin wrote:
>
> 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 ?

ok

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

When the tyrant has disposed of foreign enemies by conquest or treaty, and
there is nothing more to fear from them, then he is always stirring up
some war or other, in order that the people may require a leader. -- Plato
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