- June 10, 2002:
The cart chunk format has now been formally ratified
by the AES Standards Committee and is now designated as AES46-2002.
The final standard icludes some minor editorial revisions (refer
for more details
- March 10, 2002:
The AES Standards Committee has started the formal
public call-for-comment period, lasting 90 days. During this time
any commenbts regarding changes to the standard must be submitted
through the formal comment review process as described in the
AES standards procedures. If no adverse comments are received
during this period, the next step will be formal adoption
- December 6, 2001:
Several changes and additions were made to
ensure the information presented on this website
regarding AES standards status and business were in
compliance with the standards process.
- December 4, 2001:
The WaveView utility has
been upgraded to properly handle odd chunk sizes.
- December 2, 2001:
The AES SC06-01 standards committee met at
the AES convention in New York. where final updates were
discussed. As soon as more information is available from
the AES, we'll update this site.
A further important update: Ed MacKenty has stepped in to
provide web support services for the cart chunk web site,
including hosting the site. "Mack" is someone
who we have worked closely with over the last several
years, and we are excited that Mack has volunteered his
services and facilities for this purpose. Thanks, Mack!
- September 19,
2001: We have uploaded a trial version of
the WaveView utility for viewing and
analyzing common chunks within Wave files, including cart
and EBU broadcast wave information. We have also uploaded
a sample wave file that's compliant with version 01.01 of
the cart specification.
- August 20, 2001: A
proposed working group draft of the cart chunk standard
has been published to the AES SC-06-01 Working Group for
their comments and correction as "AES
standard for network and file transfer of audio -
Audio-file transfer and exchange - Radio traffic audio
delivery extension to the broadcast WAVE file format,"
a.k.a. AES-46. Some significant changes to the document
were required to meet the documentation standards. None
of these changes materially effect the actual data.
The secretariat, in preparing the document for draft
release, made a small number of comments, one of which
has a potential for materially affecting the data format.
Their sugggestion was to make the time and data strings,
e.g., StartDate, StartTime, EndDate,
and EndTime conform to the appropriate ISO
standard for date and time presentation. Following the
example of AES31-3, the description of the data and time
formats may be changed to be compliant with ISO8601,
which limits date field separator characters to
"/" and time field separators to ":".
The original cart chunk spec followed the lead of the EBU
3285 Broadcast Wave Extension, which allowed any number
of non-alphanumeric field separators.
The change, at the force of a recommendation and not a
requirement, would restrict date formats to the
recommendations of ISO8601, e.g., "2001-08-20"
- May 21, 2001: The
AES Standards Committee SC-06-01 met at the 110th AES
Convention in Amsterdam on May 11, 2001. At that meeting,
the status of the Cart Chunk standard AES Project X87 was
raised. It was reported that no adverse comments were
received by the working group since the last meeting, and
the proposal is being prepared for the call-for-comment
process as AES-46. For more details, including the latest
AES official status, check out SC-06-01 committee report, on the the AES Standards web site.
- March 5, 2001: New
vendor information has been added to the website, and the
current state of the standards process has been updated.
- February 1, 2001:
The Cart Chunk document was edited to
conform more closely with AES standards requirements,
explanatory notes were removed as required, and the final
draft submitted. Currently, we are awaiting the start of
the "call for comment" period before
Please note that the document submitted to and approved
by the AES will be considered as the "official"
- September 30,
2000: At the most recent meeting of the AES
SC06-01 Subcommittee on File Formats, the latest proposal
for the Cart Chunk standard was submitted as AES Project
X87. No objections were raised by any committee members,
and the current intent is to move it to the Call for
Comment phase as soon as feasible.
- August 15, 2000:
Currently, there is an active
discussion on finalizing the addition of URL field to the
Cart chunk before going to the finalization of the
standard. The URL field will allow the inclusion of a
relevant URL linked to the audio directly. A URL could be
used, for example, as a hyperlink in a commercial to an
advertiser's web site, in a music spot as a pointer to
the composer/artist's web site, in a news spot as a
pointer to more details about the story, etc..
We have discussed this with several parties and are
proposing the following modification to the Cart Chunk
- The contents of the Version
field shall be incremented to reflect a new version
of the structure. This will allow applications to
differentiate between the new and prior versions of
the structure. The first released version was tagged
as "0100" corresponding to version 1.00.
The additions describe here shall constitute version
1.01, and the Version field will be
set at "0101" accordingly.
- The current Reserved
field shall remain as described. This shall be
available for future utilization by compact data.
This, for example, would allow expansion of the PostTimers
array if needed.
- The new URL field
shall immediately follow the Reserved
array field and be 1024 bytes long.
The URL field contents shall meet
the "Internet Official Protocol Standards (STD
1), Uniform Resource Identifiers (URI) Generic
Syntax" as described in RFC2396. If the URL/URI
string is less than 1024 bytes in length, it shall be
terminated by a null byte, and the terminator and the
remainder of the 1024 byte field shall be ignored.
- The TagText field
will start immediately following the URL
field, and be utilized as before. The only difference
is its starting point in the cart Chunk.
The resulting cart data structure would
then be (the modified or new fields are highlighted in red and
/* Version of
the data structure */
title of cart audio sequence */
ASCII artist/creator name
/* ASCII cut
number identification */
ASCII client identification
ASCII Category ID, PSA, NEWS, etc */
CHAR Classification; /* ASCII
Classification/auxiliary key */
out cue text
/* ASCII yyyy/mm/dd
/* ASCII yyyy/mm/dd
/* ASCII hh:mm:ss
CHAR ProducerAppID; /* Name of
CHAR ProducerAppVersion; /* Version of
producer application */
/* User defined text
DWORD dwLevelReference; /* Sample
value for 0 dB reference */
CART_TIMER PostTimer; /* 8 time markers
/* Reserved for future expansion
/* ASCII text for scripts or tags
The change results in a 2048-byte size
for the Cart Chunk data area, not including the optional TagText
data. Given that WAVE files of several megabytes are routine,
this increase is insignificant at best. Applications shall
determine from the Version field whether the new URL
field is present, and from the chunk size whether TagText
is present as well. (note that one consensus of the group is
that the TagText field is considered
relatively unimportant: not a small number of respondants
said that their produce applications did not add TagText
information, while consumer applications ignored it if it was
present. Only a single application of those sampled utilized
the TagText field, thus the increment in
version number is required to ensure backwards and forwards
We have arrived at this consensus after
discussing this with several vendors and users who are
already using the Cart Chunk. We believe that it represents
the best copromise and provides a high degree of both
forwards and backwards compatibility at the lowest
development and implementation cost.
The method we propose here can be used
in the future for expansion: the version number shall
indicate which form of the structure is in use, and new
fields shall be added before the TagText,
which shall always be found following the last defined field
of the structure (in the present proposal, the URL field).
We will attempt to have this addition
finalized and ready for the next stage of standardization.
We welcome your comments and suggestions.
Contact us for if you wish to contribute to this and other
processes regarding the Cart Chunk.