Converting DASHhigh to FLAC with ffmpeg

[RS]

>From: Budge Sent: Wednesday, January 25, 2017 00:04

>I am certain I shall not be able to hear the differences if a young chap 
>like you cannot.  When I find out how, in detail, I shall try converting 
>some samples to mp3 and thanks for the further nudge in that direction.

I started this thread as a reference on how to convert AAC to FLAC, because 
I had not found it obvious.  If anyone wants a preset to do it, it is at the 
beginning of this thread.  If anyone wants a preset to convert to MP3, refer 
to the wiki
https://github.com/get-iplayer/get_iplayer/wiki/documentation
under Option Presets and Shortcuts.

The thread has turned into a discussion of hearing capabilities.  It may be 
possible to hear a slight difference between 128kbit/s AAC/M4A and 128kbit/s 
MP3.  Those who say there is no audible difference between 320kbit/s AAC/M4A 
and 320kbit/s MP3 are probably right.  Amazon has been selling music as 
320kbit/s MP3 files for several years, and I have not seen complaints about 
quality in the reviews.

Converting to FLAC of course cannot improve quality.  The reason for 
converting to FLAC, for those whose players support FLAC and are having 
difficulty playing some AAC files, which seems to include the Linn player 
and my £19 AGPtEK player, is that it is an option for making the files 
playable.  The other option is to convert them to MP3 at a bit rate 
appropriate for the material.

The disadvantage of converting to FLAC is that the files are 50% or more 
larger.

The advantages of converting to FLAC are
1.  In my limited tests with ffmpeg the conversion is about 7 times as fast, 
although that depends on the codec.
2.  There is no need to keep the AAC/M4A original, because a perfect copy 
can be created from the FLAC file.

If you convert to 320kbit/s MP3 you will probably want to keep the AAC file, 
because if you need to convert the MP3 back to AAC it is a bit like 
photocopying a photocopy.