[FFmpeg-user] Measuring received stream quality

Carl Eugen Hoyos cehoyos at ag.or.at
Thu Feb 7 18:55:07 CET 2013

Miguel Matos <razielukain <at> gmail.com> writes:

> The log produced when the stream received is not 'perfect' 
> contains a bunch of errors like "end mismatch left=4677 147B52" 
> and "concealing 520 DC, 520 AC, 520 MV errors in P frame".
> I would like some pointers or explanation on the meaning of 
> these errors, namely what they semantically mean and what's 
> behind values like 520 DC and so on.

I can only tell you that MV probably stands for motion vector.

> Ideally, I would like to have some kind of measurement of the 
> quality of the received stream and answer some questions like:
> - does no errors reported imply the stream was played crystal 
> clear ?

Please define "crystal clear".

> - is it possible to create a mapping of the errors/amount of 
> errors to a better metric like the number of 
> unplayable/unviewable frames ?

The number should be 0 in nearly all cases because FFmpeg by 
default uses error concealment.
(I believe you get a specific error if a frame gets completely 

> Note that visual inspection of the video does not work 
> because we need some quantifiable metric, just a 'looks good' 
> is not enough.

I don't think what you want is currently implemented in FFmpeg, 
but I am not completely sure that it is possible in general 
(in a way that actually makes sense).

Your transport layer should easily allow to tell you about lost 
information though.

Carl Eugen

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