[FFmpeg-devel] [PATCH] ACT demuxer

[Vladimir Voroshilov]

Hi, Michael

On Mon, Feb 25, 2008 at 6:41 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Mon, Feb 25, 2008 at 01:16:48PM +0600, Vladimir Voroshilov wrote:
>  > Hi, Michael
>  >
>  > On Mon, Feb 25, 2008 at 12:36 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
>  >
>  > > [...]
>  >
>  > >  > +{
>  > >  > +    int score=0;
>  > >
>  > > > +
>  > >  > +    if ((AV_RL32(&p->buf[0]) != RIFF_TAG) ||
>  > >  > +        (AV_RL32(&p->buf[8]) != WAVE_TAG) ||
>  > >  > +        (AV_RL32(&p->buf[16]) != 16))
>  > >  > +    return 0;
>  > >  > +
>  > >
>  > >  > +    if(match_ext(p->filename, "act"))
>  > >  > +        score=AVPROBE_SCORE_MAX/4;
>  > >
>  > >  iam against this, if detection is done based on the filename
>  > >  then theres no need for act_probe()
>  > >

Filename check removed

>  [...]

>  > 3. bytes 44-256 and 264-511 are filled by zero (not reliable too)
>
>  Do you have an act file which contains non zero bytes there? If not these
>  could be checked as well.

Never seen such files.

>  > 4. the rest are 512 bytes long chunks with 2 of 6 zero-filled padding
>  > data at the end (unable to differ from WAV data).
>  >
>  > So there is no reliable method for format detection.
>  > We always can create correct WAV file which will look like ACT
>
>  Yes, but luckily we dont need a 100% reliable check, we just need one
>  which is sufficiently reliable, checking 2 bytes where one (the size) has
>  a very high chance of matching a valid wav, could easily lead to
>  1 misdetectionsin in 1000.
>  Checking 10 bytes would if half of them are random give better than
>  1 misdetection in 2^40.

If attached version better?
It also checks zero bytes after WAV header and after ACT
data at the middle of header.

av_set_pts fixed as suggested by you.
4400 format disabled until sample file of info from disassembled code
will be available.

-- 
Regards,
Vladimir Voroshilov     mailto:voroshil at gmail.com
JID: voroshil at gmail.com, voroshil at jabber.ru
ICQ: 95587719
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