Re: OPUS/FLAC Metadata

On 16 Jun 2017, at 18:30, Romain Beauxis wrote:

> 2017-06-16 10:28 GMT-05:00 Jesus Cea <[email protected]>:
>> On 16/06/17 13:18, Marvin Scholz wrote:
>>> The source client is supposed to encode the metadata into the stream,
>>> not use any endpoint whatsoever to send them, for Ogg and
>>> other supported formats. There is nothing confusing about this. The
>>> reason this is different for MP3 and AAC is, that it is simply
>>> impossible to do that for these formats, which is why the endpoint you
>>> mentioned exists. Kind of a hack to workaround the limitations
>>> of the formats.
>>
>> Reading OPUS OGG fileformat, the metadata is limited to the second
>> "page". In a live-stream, you could not send a new metadata
>> information... unless you send a logical "End of Stream" to the icecast
>> server followed by a new "Start of Stream" followed by new metadata. I
>> wonder if that is transparent to the client, because the client I use
>> stops reproducing when finding the EOS mark.
>>
>> So, how OPUS metadata updates works?
>>
>> I am deploying a new radio streaming service and I would love to use
>> OPUS streaming, but I don't understand how to send metadata updates to
>> icecast, how it send them to the clients and, moreover, current Debian
>> supported version is 2.4.0 (I could override that, of course).
>>
>> That is, saying that OPUS metadata is embedded in the stream is
>> insufficient, because OPUS OGG specification clearly indicates that
>> metadata is ONLY legal at the very beginning of the file.
>>
>> Please, provide more details.
>>
>> * How source EXACTLY communicates metadata updates to the server? "Embed
>> it in the stream" is not enough information.
>>
>> * How are those updates send to the clients?. Using legacy ICY?, OGG
>> embedding?. How it works in that case, because OGG only supports
>> metadata at the beginning of the stream, and stream concatenation (an
>> EOS followed with a Start Of Stream) is not supported by many clients...
>
> As far as I know, EOS followed by a new stream is the only way to pass
> metadata in ogg-embedded streams. Clients didn't support that very well
> back some years ago but I would hope that this is better now.. Only other
> alternative to avoid stream concatenation is to remove all subsequent
> metadata, I'm afraid.

This concatenation are valid streams, it's called chaining, afaik. So
players not supporting them are broken and the authors should be
notified about it, I think.

>
> Romain
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