ogg dev - Jun 2012 - Fwd: Additional ogg audio fomats (speex, flac, PCM)

Hi

After much googling, am struggling to find either:

a) a command-line utility that allows me to encode to non-vorbis ogg audio
(*nix)
b) example files of the above

Am building a program part of which reads stream meta from uploaded audio
files, and so have written a lightweight getid3-like set of classes that do
this. Am handling ogg vorbis perfectly well already and would like to test
it against the others.

Additionally (out of pure interest) does anyone know of good literature
pertaining to examples of (ab)using libogg to package arbitrary audio
formats?

Many thanks
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On Sat Jun  2 07:19:14 2012, clancy hood wrote:
> a) a command-line utility that allows me to encode to non-vorbis ogg
> audio (*nix)
There's not really a single utility. You can make .spx files
(speex-in-ogg) with speexenc, ogg flac files with 'flac --ogg', and
.opus files (opus-in-ogg) with opusenc.
> b) example files of the above
You can get an example opus file (with metadata) at
http://people.xiph.org/~giles/2012/opus/ehren-paper_lights-64.opus

You can find some speex file e.g. at
http://people.xiph.org/~giles/2008/lca/mirror/Wed/

Ogg Flac isn't very popular; it's mostly useful for muxing with video. I
don't have any examples handy.

No one uses ogg pcm at all. I think there are some experimental
implementations, but I don't remember where they are. I wouldn't
worry about that one.
> Am building a program part of which reads stream meta from uploaded
> audio files, and so have written a lightweight getid3-like set of
> classes that do this. Am handling ogg vorbis perfectly well already
> and would like to test it against the others.
Neat. Have you looked at calculating the file length so you can set the
Content-Duration header when serving the files back?
> Additionally (out of pure interest) does anyone know of good
> literature pertaining to examples of (ab)using libogg to package
> arbitrary audio formats?
We generally discourage this, since our mission is to provide
royalty-free, libre multimedia technology. However, if you have a
specific audio format in mind, this is a good place to talk about the
best way to define an Ogg encapsulation method.

HTH and thanks for supporting Ogg,
 -r

[Woops, forgot to reply to the list ; just sent the following to Ralph]

Thankyou guys.
> All Speex files (.spx) are encoded in Ogg, so speexenc is all you need
for that.
> The standard "flac" utility will encode into Ogg with the --ogg
switch.
D'oh! Have been RTFM'ing an awful lot lately, but I completely missed
that
flac has an --ogg switch
> You may also wish to support Opus
Great, thanks will take a look
> No one uses ogg pcm at all. I think there are some experimental
implementations,
but I don't remember where they are. I wouldn't worry about that one.

No, I suppose FLAC itself would render that option somewhat obsolete, and
as you say people tend not to package flacs in oggs. Advice taken.

Thankyou also for the example files and the opus links.
> Neat. Have you looked at calculating the file length so you can set the
Content-Duration
header when serving the files back?

Yes, I already do. Stream meta is dumped in a database,
non-compressed/lossless formats are transcoded to flac to be stored, and
subsequent requests may be made for the file in an arbitrary format,
depending on user settings. The content-duration header is always sent,
indeed some browsers struggle without it. However, some clients (particularly
Chrome it seems) will request byte-ranges when playing an ogg, and am
slightly confused as to whether I should return a content-duration header
whilst satisfying a byte-range request, or only during the first request.
At the moment I send it every time, and no damage appears to be done.

Incidentally, whilst the documentation is excellent, there are one or 2
things I am slightly confused about, if you don't mind my going off-topic:

1) It seems I can always rely on the first byte of the first vorbis comment
page to be 3. Is this right?
I see that some pages begin with a byte and then "vorbis", but
haven't yet
found a resource that tells me what that byte means.

2) In fact, must page 2 of an ogg be a comment page, or may it be missing
altogether? So far, I've found "empty" pages with a single page
segment,
but never a missing comment page.

In case you're interested, the overall intention of this part of the
program is thus: when inputting the file, it must read the stream meta,
comments etc in order to dump them in a database. When outputting the file,
the requested stream may include additional comment data which the user
intends to be included with the file, so in e.g. an ogg stream request, the
transcoded ogg file will have its (empty, if any) comment pages replaced
with pages created by my program on the fly. This is in order that I may
cache transcoded files and comments separately, since comments may change
but a transcoded file will not (am aware of the stream_serial_number
problem this gives me, btw). This means am currently getting to grips with
the bones of ogg's page structure quite intimately, and getting hold of /
creating some variations in the layout will help me unit-test the parsing
side of things as well as open up possibilities on the streaming side,
hence my original message.




On 2 June 2012 16:10, Ralph Giles <giles at thaumas.net> wrote:
> On Sat Jun  2 07:19:14 2012, clancy hood wrote:
>
> > a) a command-line utility that allows me to encode to non-vorbis ogg
> > audio (*nix)
>
> There's not really a single utility. You can make .spx files
> (speex-in-ogg) with speexenc, ogg flac files with 'flac --ogg', and
> .opus files (opus-in-ogg) with opusenc.
>
> > b) example files of the above
>
> You can get an example opus file (with metadata) at
> http://people.xiph.org/~giles/2012/opus/ehren-paper_lights-64.opus
>
> You can find some speex file e.g. at
> http://people.xiph.org/~giles/2008/lca/mirror/Wed/
>
> Ogg Flac isn't very popular; it's mostly useful for muxing with
video. I
> don't have any examples handy.
>
> No one uses ogg pcm at all. I think there are some experimental
> implementations, but I don't remember where they are. I wouldn't
> worry about that one.
>
> > Am building a program part of which reads stream meta from uploaded
> > audio files, and so have written a lightweight getid3-like set of
> > classes that do this. Am handling ogg vorbis perfectly well already
> > and would like to test it against the others.
>
> Neat. Have you looked at calculating the file length so you can set the
> Content-Duration header when serving the files back?
>
> > Additionally (out of pure interest) does anyone know of good
> > literature pertaining to examples of (ab)using libogg to package
> > arbitrary audio formats?
>
> We generally discourage this, since our mission is to provide
> royalty-free, libre multimedia technology. However, if you have a
> specific audio format in mind, this is a good place to talk about the
> best way to define an Ogg encapsulation method.
>
> HTH and thanks for supporting Ogg,
>  -r
>
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clancy hood wrote:
> [Woops, forgot to reply to the list ; just sent the following to Ralph]
No worries, I've been doing this for years and I still managed to send 
you my reply off-list. I hate that particular configuration of our lists.
> 1) It seems I can always rely on the first byte of the first vorbis
> comment page to be 3. Is this right?
> I see that some pages begin with a byte and then "vorbis", but
haven't
> yet found a resource that tells me what that byte means.
This is explained in the Vorbis spec: 
http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-610004.2.1
> 2) In fact, must page 2 of an ogg be a comment page, or may it be
> missing altogether? So far, I've found "empty" pages with a
single page
> segment, but never a missing comment page.
The second packet of a Vorbis stream must always be a comment header. It 
isn't legal to omit it. It can span multiple pages (and will sometimes 
do so when people embed album art in it).

>> [Woops, forgot to reply to the list ; just sent the following to Ralph]
> No worries, I've been doing this for years and I still managed to send 
you my reply off-list. I hate that particular configuration of our lists.
:)  and then I got your reply on the list archive, but not in my inbox
- supposedly since I'm subscribed to "digests", I wouldn't
have gotten
it til later, even though I started the thread ...
> This is explained in the Vorbis spec:
http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-610004.2.1
Thankyou. I shall try to RTFM with more care from here on.
> The second packet of a Vorbis stream must always be a comment header. It
isn't legal to omit it. It can span multiple pages (and will sometimes do so
when people embed album art in it).
Brilliant.

Many thanks
C



On 2 June 2012 17:53, clancy hood <clancyhood at gmail.com>
wrote:
>
> [Woops, forgot to reply to the list ; just sent the following to Ralph]
>
> Thankyou guys.
>
> > All Speex files (.spx) are encoded in Ogg, so speexenc is all you need
for that.
> > The standard "flac" utility will encode into Ogg with the
--ogg switch.
>
> D'oh! Have been RTFM'ing an awful lot lately, but I completely
missed that flac has an --ogg switch
>
> >?You may also wish to support Opus
>
> Great, thanks will take a look
>
> >?No one uses ogg pcm at all. I think there are some
experimental?implementations, but I don't remember where they are.?I
wouldn't?worry about that one.
>
> No, I suppose FLAC itself would render that option somewhat obsolete, and
as you say people tend not to package flacs in oggs. Advice taken.
>
> Thankyou also for the example files and the opus links.
>
> >?Neat. Have you looked at calculating the file length so you can set
the?Content-Duration header when serving the files back?
>
> Yes, I already do. Stream meta is dumped in a database,
non-compressed/lossless formats are transcoded to flac to be stored, and
subsequent requests may be made for the file in an arbitrary format, depending
on user settings. The content-duration header is always sent, indeed some
browsers struggle without it. However, some clients?(particularly Chrome it
seems)?will request byte-ranges when playing an ogg, and am slightly confused as
to whether I should return a content-duration header whilst satisfying
a?byte-range request, or only during the first request. At the moment I send it
every time, and no damage appears to be done.
>
> Incidentally, whilst the documentation is excellent, there are one or 2
things I am slightly confused about, if you don't mind my going off-topic:
>
> 1) It seems I can always rely on the first byte of the first vorbis comment
page to be 3. Is this right?
> I see that some pages begin with a byte and then "vorbis", but
haven't yet found a resource that tells me what that byte means.
>
> 2) In fact, must page 2 of an ogg be a comment page, or may it be missing
altogether? So far, I've found "empty" pages with a single page
segment, but never a missing comment page.
>
> In case you're interested, the overall intention of this part of the
program is thus: when inputting the file, it must read the stream meta, comments
etc in order to dump them in a database. When outputting the file, the requested
stream may include additional comment data which the user intends to be included
with the file, so in e.g. an ogg stream request, the transcoded ogg file will
have its (empty, if any) comment pages replaced with pages created by my program
on the fly. This is in order that I may cache transcoded files and comments
separately, since comments may change but a transcoded file will not (am aware
of the stream_serial_number problem this gives me, btw). This means am currently
getting to grips with the bones of ogg's page structure quite intimately,
and getting hold of / creating some variations in the layout will help me
unit-test the parsing side of things as well as open up possibilities on the
streaming side, hence my original message.
>
>
>
>
> On 2 June 2012 16:10, Ralph Giles <giles at thaumas.net> wrote:
>>
>> On Sat Jun ?2 07:19:14 2012, clancy hood wrote:
>>
>> > a) a command-line utility that allows me to encode to non-vorbis
ogg
>> > audio (*nix)
>>
>> There's not really a single utility. You can make .spx files
>> (speex-in-ogg) with speexenc, ogg flac files with 'flac --ogg',
and
>> .opus files (opus-in-ogg) with opusenc.
>>
>> > b) example files of the above
>>
>> You can get an example opus file (with metadata) at
>> http://people.xiph.org/~giles/2012/opus/ehren-paper_lights-64.opus
>>
>> You can find some speex file e.g. at
>> http://people.xiph.org/~giles/2008/lca/mirror/Wed/
>>
>> Ogg Flac isn't very popular; it's mostly useful for muxing with
video. I
>> don't have any examples handy.
>>
>> No one uses ogg pcm at all. I think there are some experimental
>> implementations, but I don't remember where they are. I
wouldn't
>> worry about that one.
>>
>> > Am building a program part of which reads stream meta from
uploaded
>> > audio files, and so have written a lightweight getid3-like set of
>> > classes that do this. Am handling ogg vorbis perfectly well
already
>> > and would like to test it against the others.
>>
>> Neat. Have you looked at calculating the file length so you can set the
>> Content-Duration header when serving the files back?
>>
>> > Additionally (out of pure interest) does anyone know of good
>> > literature pertaining to examples of (ab)using libogg to package
>> > arbitrary audio formats?
>>
>> We generally discourage this, since our mission is to provide
>> royalty-free, libre multimedia technology. However, if you have a
>> specific audio format in mind, this is a good place to talk about the
>> best way to define an Ogg encapsulation method.
>>
>> HTH and thanks for supporting Ogg,
>> ?-r
>
>
>