[FFmpeg-devel] AC3 Format Detection unreliable.
Justin Ruggles
justinruggles
Sun Aug 5 02:33:03 CEST 2007
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
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