Combination of Tips

Some days I am more clever than others. Today, I was working on digitizing about 50 older (30 years old) cassettes for a linguist. To organize the data I have need of creating a folder for each tape. Each folder needs to be sequentially numbered. It is a lot of tedious work - not something I enjoy.

So I looked up a few things in terminal to see if I could speed up the process. I needed to create a few folders so I looked up on hints MacWorld:

So I looked at the mkdir command, which creates new folders or directories. It uses the following syntax: mkdir folder1 folder2 folder3

Now I needed a list of the folders I needed... something like 50.

So I created a formula in a google spreadsheet using the Concatenate command. I was able in one column to add the Alpha characters I needed and in the next column I was able to add the sequential numerics I needed.

Now I had a list of 50 names of my folders, but I still needed to remove the return characters which separated them from each other to allow the mkdir command to work. So I opened up TextEdit and did a search for return tabs in the document and deleted them.

Now I could just paste the 50 folder names in terminal and hit enter and it created 50 folders... But I wonder if there was a way to add sequential numbers to a base folder-name in terminal without using google spreadsheets...

Audio Dominant Texts and Text Dominant Audio

As linguistics and language documentation interface with digital humanities there has been a lot of effort to time-align texts and audio/video materials. At one level this is rather trivial to do and has the backing of comercial media processes like subtitles in movies. However, at another level this task is often done in XML for every project (digital corpus curation) slightly differently. At the macro-scale the argument is that if the annotation of the audio is in XML and someone wants to do something else with it, then they can just convert the XML to whatever schema they desire. This is true.

However, one antidotal point that I have not heard in discussion of time aligned texts is specifications for Audio Dominant Text vs. Text Dominant Audio. This may not initially seem very important, so let me explain what I mean.
Continue reading

Presenting Audio and Video on the Web

I have been trying to find out what is the best way to present audio on the web. This led me to look at how to present video too. I do not have any conclusions on the matter. But I have been looking at HTML5 and not using javascript or Flash. Because my platform (CMS) is WordPress, Continue reading

Finding your inner Zachman

The last couple of weeks I have been working on applying the Zachman's framework for enterprise architecture to two projects. I have been struggling through the first row and then skipped around a bit. I think I have found the part of the project (any project) I am most passionate about.... Working with Human Interface Architecture and explaining it as a designer to the builder of the Presentation Architecture. In my mind this level needs to be closely related to the Business Process Model and to the List of Business Goals/Strategies.

Where do I see myself most helpful in the large project...

Presentation version vs. Archival version of Digital Audio files

What is an archival version of an audio file?

An archival version of an audio file is a file which represents the original sound faithfully. In archiving we want to keep a version of the audio which can be used to make other products and also be used directly itself if needed. This is usually done through PCM. There are several file types which are associated with PCM or RAW uncompressed faithful (to the original signal) digital audio. These are:

  • Standard Wave
  • AIFF
  • Wave 64
  • Broadcast Wave Format (BWF)One way to understand the difference between audio file formats is understanding how different format are used. One place which has been helpful to me has been the DOBBIN website as they explain their software and how it can change audio from one PCM based format to another.

Each one of these file types has the flexibility to have various kinds of components. i.e. several channels of audio can be in the same file. Or one can have .wav files with different bit depths or sampling rates. But they are each a archive friendly format. Before one says that a file is suitable for archiving simply based on its file format one must also consider things like sample rates, bit depth, embedded metadata, channels in the file, etc. I was introduced to DOBBIN as an application resource for audio archivists by a presentation by Rob Poretti. One additional thing that is worth noting in terms of archival versions of digital audio pertains to born digital materials. Sometimes audio is recored directly to a lossy compressed audio format. It would be entirely appropriate to archive a born-digital filetype based on the content. However it should be noted that in this case the recordings should have been done in a PCM file format.

What is a presentation version? (of an audio file)

A presentation version is a file created with a content use in mind. There are several general characteristics of this kind of file:

  1. It is one that does not retain the whole PCM content.
  2. It is usually designed for a specific application. (Use on a portable device, or personal audio player)
  3. It can be thought of as a derivative product from an original audio or video stream.

In terms of file formats, there is not just one file format which is a presentation format. There are many formats. This is because there are many ways to use audio. For instance there are special audio file types optimized for various kinds of applications like:

  • 3G and WiFi Audio and A/V services
  • Internet audio for streaming and download
  • Digital Radio
  • Digital Satellite and Cable
  • Portable playersA brief look a an explanation by Cube-Tec might help to get the gears moving. It is part of the inspiration for this post.

This means there is a long list of potential audio formats for the presentation form.

  • AAC (aac)
  • AC3 (ac3)
  • Amiga IFF/SVX8/SV16 (iff)
  • Apple/SGI (aiff/aifc)
  • Audio Visual Research (avr)
  • Berkeley/IRCAM/CARL (irca)
  • CDXA, like Video-CD (dat)
  • DTS (dts)
  • DVD-Video (ifo)
  • Ensoniq PARIS (paf)
  • FastTracker2 Extended (xi)
  • Flac (flac)
  • Matlab (mat)
  • Matroska (mkv/mka/mks)
  • Midi Sample dump Format (sds)
  • Monkey’s Audio (ape/mac)
  • Mpeg 1&2 container (mpeg/mpg/vob)
  • Mpeg 4 container (mp4)
  • Mpeg audio specific (mp2/mp3)
  • Mpeg video specific (mpgv/mpv/m1v/m2v)
  • Ogg (ogg/ogm)
  • Portable Voice format (pvf)
  • Quicktime (qt/mov)
  • Real (rm/rmvb/ra)
  • Riff (avi/wav)
  • Sound Designer 2 (sd2)
  • Sun/NeXT (au)
  • Windows Media (asf/wma/wmv)

Aside from just the file format difference in media files (.wav vs. .mp3) there are three other differences to be aware of:

  1. Media stream quality variations
  2. Media container formats
  3. Possibilities with embedded metadata

Media stream quality variations

Within the same file type there might be a variation of quality of audio. For instance Mp3 files can have a variable rate encoding or they can have a steady rate of encoding. When they have a steady rate of encoding they can have a High or a low rate of encoding. WAV files can also have a high or a low bit depth and a high or a low sample rate. Some file types can have more channels than others. For instance AAC files can have up to 48 channels where as Mp3 files can only have up to 5.1 channels.

One argument I have heard in favor of saving disk space is to use lossless compression rather than WAV files for archive quality (and as archive version) recordings. As far as archiving is concerned, these lossless compression formats are still product oriented file formats. One thing to realize is that not every file format can hold the same kind of audio. Some formats have limits on the bit depth of the samples they can contain, or they have a limit on the number of audio channels they can have in a file. This is demonstrated in the table below, taken from wikipedia. This is where understanding the relationship between a file format, a file extension and a media container format is really important.

Audio compression formatAlgorithmSample RateBits per sampleLatencyStereoMultichannel
ALACLossless44.1 kHz to 192 kHz16, 24[41]?YesYes
FLACLossless1 Hz to 655350 Hz8, 16, 20, 24, (32)4.3ms - 92ms (46.4ms typical)YesYes: Up to 8 channels
Monkey's AudioLossless8, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48 kHz??YesNo
RealAudio LosslessLosslessVaries (see article)Varies (see article)VariesYesYes: Up to 6 channels
True AudioLossless0–4 GHz1 to > 64?YesYes: Up to 65535 channels
WavPack LosslessLossless, Hybrid1 Hz to 16.777216 MHzvaries in lossless mode; 2.2 minimum in lossy mode?YesYes: Up to 256 channels
Windows Media Audio LosslessLossless8, 11.025, 16, 22.05, 32, 44.1, 48, 88.2, 96 kHz16, 24>100msYesYes:Up to 6 channels

Media container formats

Media container formats can look like file types but they really are containers of file types (think like a folder with an extension). Often they allow for the bundling of audio and video files with metadata and then enable this set of data to act like a single file. On wikipedia there is a really nicecomparison of container formats.

MP4 is one such container format. Apple Lossless data is stored within an MP4 container with the filename extension .m4a – this extension is also used by Apple for AAC audio data in an MP4 container (same container, different audio encoding). However, Apple Lossless is not a variant of AAC (which is a lossy format), but rather a distinct lossless format that uses linear prediction similar to other lossless codecs such as FLAC and Shorten. Files with a .m4a generally do not have a video stream even though MP4 containers can also have a video stream.

MP4 can contain:

  • Video: MPEG-4 Part 10 (H.264) and MPEG-4 Part 2
    Other compression formats are less used: MPEG-2 and MPEG-1
  • Audio: Advanced Audio Coding (AAC)
    Also MPEG-4 Part 3 audio objects, such as Audio Lossless Coding (ALS), Scalable Lossless Coding (SLS), MP3, MPEG-1 Audio Layer II (MP2), MPEG-1 Audio Layer I (MP1), CELP, HVXC (speech), TwinVQ, Text To Speech Interface (TTSI) and Structured Audio Orchestra Language (SAOL)
    Other compression formats are less used: Apple Lossless
  • Subtitles: MPEG-4 Timed Text (also known as 3GPP Timed Text).
    Nero Digital uses DVD Video subtitles in MP4 files

This means that an .mp3 file can be contained inside of an .mp4 file. This also means that audio files are not always what they seem to be on the surface. This is why I advocate for an archive of digital files which archives for a digital publishing house to also use technical metadata as discovery metadata. Filetype is not enough to know about a file.

Possibilities with embedded metadata

Audio files also very greatly on what kinds of embedded metadata and metadata formats they support. MPEG-7, BWF and MP4 all support embedded metadata. But this does not mean that audio players in the consumer market or prosumer market respect this embedded metadata. ARSC has in interesting report on the support for embedded metadata in audio recording software. Aside from this disregard for embedded metadata there are various metadata formats which are embedded in different file types, one common type ID3, is popular with .mp3 files. But even ID3 comes in different versions.

In archiving Language and Culture Materials our complete package often includes audio but rarely is just audio. However, understanding the audio components of the complete package help us understand what it needs to look like in the archive. In my experience in working with the Language and Culture Archive most contributors are not aware of the difference between Archival and Presentation versions of audio formats and those who think they do, generally are not aware of the differences in codecs used (sometimes with the same file extension). From the archive’s perspective this is a continual point of user/submitter education. This past week have taken the time to listen to a few presentations by Audio Archivist from the 2011 ARSC convention. These in general show that the kinds of issues that I have been dealing with in the Language and Culture Archive are not unique to our context.

The Complete Audio Package

The Complete Audio Package

AKAI GX-220D

This past weekend I walked across the street from our house with Becky and went to an estate sale. In one of the rooms there was a stack of electronics. There on a dresser was a Reel-to-Reel machine in almost perfect condition.

AKAI GX-220D

AKAI GX-220D

The week prior I had been working with some Reels of language data in the archive. We have two machines but one of them does not work completely. Some amazing stuff. So now it sits on my desk and I am using my Marantz PMD 661 to digitize all sorts of Reel to Reels. Today I was looking up this model online and found it on Ebay for $300 and in Germany on Ebay for 500€, not bad as I paid $35 for mine. I finally found the manuals online for Free! It seems that somebody is trying to sell print offs on ebay for $11 each. But here is what I found.

Specifications

Track system: 4 track, 2 channel stereo/monaural system

Maximum reel capacity: 7″ reel

Wow and flutter: 0.08% at 7.5 ips

Frequency response: 30Hz to 24kHz at 7.5ips

Distortion: less than 1.5%

Signal to noise ratio: >50dB

Heads: 3 heads

Motors: 3 motors

Dimensions: 430 x 425 x 230mm

Weight: 19kg

One of my concerns is with the 30Hz playback.

Was this standard for reel-to-reels or was there better recordings done but I will never know because of the model of playback machine I have?

Another concern I have is about the heads:

If they are magnetized will they erase my tape? How do I tell if they are magnetized?

Here is a listing of Reel-to-Reel machines by AKAI.

Here is a youtube video of the same model I have.