[opus] Ogg Format

[Jean-Marc Valin]

On 05/11/2016 12:35 PM, Amit Ashara wrote:
> I ran the opusenc.exe on a wave file and checked the OpusTag section. My
> concern is on Total Segment Size being >> than the actual data being
> put. Is this just an example of implementation or does a size of 764
> BYTES kept as a place holder for putting more data?

Yes, opusenc does reserve some space in the header so that tags can
later be modified "in place", without having to rewrite the entire file.

	Jean-Marc


> 4f 67 67 53 = Oggs
> 00 = Version
> 00 = Header
> 00 00 00 00 00 00 00 00 = Granule Position
> a5 73 00 00 = Bit Stream Serial Number
> 01 00 00 00 = Page Sequence Numner
> 90 a9 36 42 = Checksum
> 03 = Page Segments
> ff ff fe = Each Segment Size (TOTAL SIZE IS 764 BYTES)
> 4f 70 75 73 54 61 67 73 = OpusTags
> 0b 00 00 00 = Vendor String Length of 11
> 6c 69 62 6f 70 75 73 20 31 2e 31 = "libopus 1.1"
> 03 00 00 00 = User Comment List Length of 3
> 25 00 00 00 = User Comment #0 String Length of 37
> 45 4e 43 4f 44 45 52 3d 6f 70 75 73 65 6e 63 20 66 72 6f 6d 20 6f 70 75
> 73 2d 74 6f 6f 6c 73 20 30 2e 31 2e 39 = "ENCODER=opusenc from
> opus-tools 0.1.9"
> 0a 00 00 00 = User Comment #1 String Length of 10
> 74 69 74 6c 65 3d 48 4f 4c 41 = "title=HOLA"
> 1e 00 00 00 = User Comment #2 String Length of 30
> 45 4e 43 4f 44 45 52 5f 4f 50 54 49 4f 4e 53 3d 2d 2d 6d 61 78 2d 64 65
> 6c 61 79 20 32 30 = "ENCODER_OPTIONS=--max-delay 20"
> 00 00 00... ALL THE WAY TO THE NEXT Oggs Container
> 
> Regards
> Amit
> 
> On Tue, May 10, 2016 at 10:47 PM, Ralph Giles <giles at thaumas.net
> <mailto:giles at thaumas.net>> wrote:
> 
>     On 10/05/16 02:37 PM, Amit Ashara wrote:
> 
>     > Is there a format document on the OpusTag structure? Search always shows
>     > up Vorbis but not Opus.
> 
>     The basic format is shared with Vorbis, but the 'magic signature' is
>     different ('OpusTags' instead of '0x05vorbis') and vorbis puts a 0x01
>     value in an extra byte after the last tag.
> 
>     The OpusTag packet layout is described in
>     https://tools.ietf.org/html/rfc7845.html#section-5.2
> 
>     Common tag names used for interoperability are described in the Vorbis
>     documentation. See https://www.xiph.org/vorbis/doc/v-comment.html
>     There are more extensive tag lists on some other sites.
> 
> 
> 
> 
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