LISTSERV mailing list manager LISTSERV 16.0

Help for ARSCLIST Archives


ARSCLIST Archives

ARSCLIST Archives


ARSCLIST@LISTSERV.LOC.GOV


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

ARSCLIST Home

ARSCLIST Home

ARSCLIST  May 2015

ARSCLIST May 2015

Subject:

Re: Is it time to rethink FLAC ?

From:

Dave Rice <[log in to unmask]>

Reply-To:

Association for Recorded Sound Discussion List <[log in to unmask]>

Date:

Mon, 18 May 2015 13:18:00 -0400

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (101 lines)

Btw, just remembered that I wrote this post a few years ago about being myself converted to the FLAC side by a colleague broadcast engineer: http://dericed.com/2013/flac-in-the-archives/.
Dave

> On May 18, 2015, at 1:10 PM, Dave Rice <[log in to unmask]> wrote:
> 
> Hi Tom,
>> On May 18, 2015, at 12:44 PM, Tom Fine <[log in to unmask]> wrote:
>> 
>> Hi Dave:
>> 
>> Can you put some of this in English?
> 
> Gladly.
> 
>> What is "demux" and "mux"? It sounds nasty but I assume it's an abbreviation for something?
> 
> Sorry these are short for multiplex and demultiplex. These terms are often paired with encode and decode, Muxing has to do with the container or file format whereas decoding is about the stream contained within.
> 
> So for instance you may have a WAV file but would have to demux it to know what the contents are. Then depending on what the content is you have be able to decode it (it's a two part step). Sometimes you may have a file that you can demux but has contents that you can't decode (like when Quicktime opens a player window at the right size and duration but then can't play the content). This is usually a behind the scenes assembly line.
> 
> Reto Kromer recently did a nice presentation on this, see slides 38-42 at http://www.reto.ch/training/2015/20150424/20150424.pdf.
> 
>> Also, what I think you're saying is that FLAC is just another audio CODEC, as is WAV. Both are lossless in that they do not throw off any samples or bits, and neither impart any perceptual encoding. Is that correct?
> 
> The language here is a little tricky because FLAC is often used to refer to FLAC the file format (.flac) as well as FLAC the lossless audio encoding. So FLAC is both a stream and a container, similar to MP3 I suppose. While a FLAC file will contain a FLAC encoding, the FLAC encoding may be in other file formats such as QuickTime and even WAV.
> 
>> Here's what I don't get about this discussion. Why would someone want to use FLAC as their primary lossless format rather than WAV, given that FLAC includes (and features) a data-compression scheme that inherently puts more data at risk per potentially bad sector in a storage device? Given the low cost of storage, why not opt for less data at risk per sector?
> 
> Cost is really a secondary issue compared to the fixity advantages.
> 
> This density issue is true. A flipped bit on a FLAC will have more impact than a flipped bit in PCM/WAV. On the other hand a FLAC file will use about 3 times less bandwidth, be 3 times faster to fully read or checksum, and faster to move from one disk to another. I'd suggest that moving 30 TB of data to new media has a slightly greater associated data risk than moving 10.
> 
> But the reason to use FLAC is really the next part. A flipped bit in PCM/WAV causes one sample somewhere to be different (maybe enough to make a click or it may be very hard to discern). If the archivist kept an external checksum, they may notice that the PCM/WAV file has a checksum mismatch but the PCM/WAV file makes it nearly impossible to figure out what the impact is. If the archivist has no checksum then the damage to a PCM/WAV is hard to be aware of.
> 
> A flipped bit on a FLAC will firstly create a mismatch during decoding. So reading a FLAC file should warn that the file is damaged and that the contents no longer represent what was originally encoded. Furthermore because audio frames within FLAC contain CRCs the damage is noted down to a portion of a section. I've worked with damaged FLAC files before and it is very easy to known that there is damage and pinpoint where. Because of the CRCs audio players can use error concealment (similar with the error concealment in a DAT player) to reduce the extent to which the error is noticed. I wrote a lot more about FLAC's fixity and preservation features here: http://dericed.com/papers/reconsidering-the-checksum-for-audiovisual-preservation/.
> 
> But in general I'd suggest that PCM/WAV is a more vulnerable format than FLAC. It requires a lot of external efforts to ensure that the data of a PCM/WAV is unchanged whereas these concerns are built into FLAC as a required feature. To have a FLAC simply by itself provides a means to validate that the data within purely represents the original audio that was encoded and if not where the discrepancy lies, PCM/WAV has no such features and requires potentially complex external fixity measures to try to accommodate this. With PCM/WAV an error or the need to apply error concealment is programmatically guesswork whereas the CRC and MD5 protection mechanisms of FLAC make this information very clear. Other audio formats use internal CRC protection to validate transmission such as MP3 but FLAC is one of the few preservation formats to make this feature available as well.
> Best Regards,
> Dave Rice
> 
>> -- Tom Fine
>> 
>> ----- Original Message ----- From: "Dave Rice" <[log in to unmask]>
>> To: <[log in to unmask]>
>> Sent: Monday, May 18, 2015 12:11 PM
>> Subject: Re: [ARSCLIST] Is it time to rethink FLAC ?
>> 
>> 
>>> Hi Lou,
>>> 
>>>> On May 18, 2015, at 11:49 AM, Lou Judson <[log in to unmask]> wrote:
>>>> 
>>>> I will admit to not reading the entire post, but have a question:
>>>> 
>>>> According to my understanding, FLAC is a non-lossy compression scene applied to WAV and PCM files,
>>> 
>>> A FLAC encoding isn't limited to PCM/WAV source, the input to the FLAC encoder is simply the raw audio with contextual metadata (bit depth, channel count, sample rate, etc) from another source.
>>> 
>>> For instance you could have
>>> 
>>> WAV ---demux---> PCM ---decode---> rawaudio ---encode---> FLAC codec ---mux---> FLAC file format
>>> 
>>> but you could have
>>> 
>>> MP3 ---demux---> MP3 ---decode---> rawaudio ---encode---> FLAC codec ---mux---> FLAC file format
>>> or
>>> S/PDIF ---demux---> PCM ---decode---> rawaudio ---encode---> FLAC codec ---mux---> FLAC file format
>>> 
>>> Most of my archival experience with FLAC involved no WAV file at all but the FLAC resulted directly from a digitization (analog source) or data migration (CD-R, DAT, etc).
>>> 
>>> It is just as technically feasible to digitize directly to FLAC as it is to scan documents to lossless LZW in TIFF or digitize video to JPEG2000 or FFV1. It doesn't matter what type of decoder is producing raw audio data but only the the raw audio data is the input to the FLAC encoder. NB I'm taking behind the scenes in the transcoding or recording process, it's rare that an operator would be connecting these pieces together without some form or programming.
>>> 
>>>> not a digital encoding format in itself.
>>> 
>>> I would consider FLAC as a digital encoding in itself.
>>> 
>>>> If that is so, then one must start with WAV (or other PCM format) files in order to get to FLAC. Therefore FLAC is an accessory, not a proper format.
>>> 
>>> I disagree. The raw audio data delivered to a FLAC encoder may come from any source that can provide raw audio data and the necessary metadata. This could be a WAV demuxer and PCM decoder but there is no such limitation that it must be. It could be from various digital audio transmission standards, other decoded lossless or lossy encodings, or other uncompressed audio encodings.
>>> 
>>>> If this is so, then it can only be seen as a storage format, not a recording format, and the argument is academic.
>>> 
>>> * head desk *
>>> 
>>>> Intelligent refutation is welcome.
>>> 
>>> I can refute, but the information above seems to be based on presumptions (correct me if I'm wrong). If you have a citation that claims that "FLAC is not a recording format", that "FLAC is not a digital encoding format", or that "one must start with WAV (or other PCM format) files in order to get to FLAC" than I am happy to refute.
>>> Dave Rice
>>> 
>>>> <L>
>>>> Lou Judson
>>>> Intuitive Audio
>>>> 415-883-2689
>>>> 
>>>> On May 18, 2015, at 6:39 AM, Dave Rice <[log in to unmask]> wrote:
>>>> 
>>>>> Hi all,
>>>>> 
>>>>> I was very pleased to hear that the merits of FLAC as a preservation format were again being considered by ARSC List; however most of the discussion only considered a few of its advantages over PCM/WAV such as that the openness of the format and resulting storage requirements, but the thread hasn't yet covered FLAC's preservation and fixity features over PCM/WAV.
>>> 

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

November 2020
October 2020
September 2020
August 2020
July 2020
June 2020
May 2020
April 2020
March 2020
February 2020
January 2020
December 2019
November 2019
October 2019
September 2019
August 2019
July 2019
June 2019
May 2019
April 2019
March 2019
February 2019
January 2019
December 2018
November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
December 2003
November 2003
October 2003
September 2003
August 2003
July 2003
June 2003
May 2003
April 2003
March 2003
February 2003
January 2003

ATOM RSS1 RSS2



LISTSERV.LOC.GOV

CataList Email List Search Powered by the LISTSERV Email List Manager