[FFmpeg-devel] AC3 Format Detection unreliable.

[Justin Ruggles]

Justin Ruggles wrote:
> Dan Sully wrote:
>> * Dan Sully shaped the electrons to say...
>>
>>>> Yes, please make the stream(s) available.
>> Also, I am on an amd64 system.
> 
> Doesn't look like that's an issue.  I'm getting the same thing on my 
> system.  The file is valid.  The issue seems to be the frame size. 
> 640kbps 48kHz is the largest AC3 frame size, and I think it's not 
> fitting enough frames into the probe buffer to give a positive 
> detection.  I'll look into it.

The problem with this sample is two-fold.  The first issue is that the 
probe buffer in this case is only 2048 bytes.  The frame size for this 
sample (and any others which are 640kbps & 48kHz) is 2560.  Therefore, 
only 1 frame is detected.  I changed the threshold for a score of 50 
down to 2 frames, but this doesn't help here.  After I changed to 1 
frame (at the start of the stream) it now gets a score of 50, but then a 
2nd issue occurs.

The sample is misdetected as MPEG-PS because it gets a score of 52 from 
mpegps_probe() for some odd reason.  I don't know a whole lot about the 
MPEG-PS format, so I don't think I can figure that part out...

-Justin