[FFmpeg-devel] [PATCH] lavc/flacdec: Add frame CRC calculation

James Almer jamrial at gmail.com
Sun Feb 17 02:43:28 CET 2013

On 16/02/13 9:30 PM, Michael Niedermayer wrote:
> On Sat, Feb 16, 2013 at 08:56:18PM -0300, James Almer wrote:
>> On 16/02/13 8:45 PM, Michael Niedermayer wrote:
>>> On Sat, Feb 16, 2013 at 06:07:49AM -0300, James Almer wrote:
>>>> Fixes ticket #2266
>>>> Signed-off-by: James Almer <jamrial at gmail.com>
>>> does this improve or worsen the way damaged files sound ?
>>> (the check is enabled be default if i didnt  misread teh code)
>> Like in other decoders, the damaged frame is discarded but the
>> decoding is not interrupted.
> thats not awnsering my question
> my goal here is that the default should be what sounds best, in the
> sense of a human listening to A and B and saying "i prefer A"
> loud pops, clicks and squeeks would be annoying so would be missing
> information.
> and repeating the last good audio frame could sound better than
> silence
> adding support for (non default enabled) crc checking is certainly
> ok OTOH ..
> but if its on by default theres the question if its what most people
> would prefer aka it sounds better ...

I think that depends on how damaged is the file/frame, or how long is 
the frame that's being dropped.
A single damaged byte will generate a CRC mismatch, but the difference
in the resulting audio will be pretty much unnoticeable for the human 
ear. In such case, the frame being dropped will be more noticeable.

Although to be honest, for lossless audio crc checks are pretty much 
essential and part of the whole point of being lossless.


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