Brendan Cully
2004-Aug-06 14:57 UTC
[icecast-dev] bug report w.r.t. streaming of metadata in icecast
On Thursday, 09 August 2001 at 18:08, Richard Fromm wrote:> On Tue, 7 Aug 2001, Richard Fromm wrote: > > > to clarify, the behavior that i saw was that most of the time the title > > streaming appeared in the client, but sometimes it did not. > > i think i've nailed this down. the problem is if the icecast server > starts in the middle of a song already being sourced to it. (which you > can get by starting icecast, start ices, then shutdown and restart icecast > and ices won't complain if a small amount of time passes)Ok, that's an ices bug. Ices should make sure to resend the metadata if it has to reconnect. I'll fix that soon.> one related question -- is there any easy way to find where the metadata > gets inserted into the stream, or do i basically have to continually parse > the stream if i want to extract that info? i'm seeing chunks of 4096 > bytes, and the metadata gets added at the end of some chunk. but this > doesn't necessarily correspond to a boundary between mp3 frames. given an > mp3 stream, once i found a frame boundary it's easy to keep finding those > boundaries. but i don't know how to arbitrarily find icecast chunk > boundaries if there's no delineating information.The server returns an icy-metaint header which tells where the info will be inserted. If, say, it's 4096 then you'll find the metadata after every 4096 bytes of MP3 data. Unfortunately it does not position itself on frame boundaries. -Brendan --- >8 ---- List archives: http://www.xiph.org/archives/ icecast project homepage: http://www.icecast.org/ To unsubscribe from this list, send a message to 'icecast-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
Brendan Cully
2004-Aug-06 14:57 UTC
[icecast-dev] bug report w.r.t. streaming of metadata in icecast
On Friday, 10 August 2001 at 15:14, Richard Fromm wrote:> On Fri, 10 Aug 2001, Brendan Cully wrote: > > > The server returns an icy-metaint header which tells where the info > > will be inserted. If, say, it's 4096 then you'll find the metadata > > after every 4096 bytes of MP3 data. > > that's what i originally thought was supposed to happen, which is why i > sent the original mail with a bug report, saying i was expecting periodic > insertion of metadata (icy-metaint was what i assumed indicated how > often), but what was really happening was that the data got inserted once > (or sometimes zero times, as per what you say and indeed sounds like an > ices bug, not an icecast bug). > > i just want to clarify, though -- it does *not* get periodically inserted > every 4096 bytes (in this instance), and that is the intention. it will > get inserted once on some 4096 byte boundary, whenever a new client > connects to the server. and it will get reinserted once for any new > client. and it will also get reinserted whenever the source tells > icecast to update the metadata, which is typically when it switches to > a new song. yes? > > sorry if i'm taking up so much e-mail on what once i understand it is i > think a reasonably simple issue.There are updates every interval. Please notice the 'justnull' variable. Apparently you haven't fully understood the format of the metadata: the first byte of metadata is a length byte. Multiply it by 16 to determine how much text to extract from the stream as metadata. If the first byte is null, then you extract 0 bytes and continue to use the metadata you already have. Every 4096 bytes you either get new metadata if the udpseqnr doesn't match between source and client, or you get a 'null' length byte. You can't just omit the data without causing skipping problems - valid mp3 data would be interpreted as a length byte and that amount of data would be removed from the stream. This should have been clear from inspection of the code. That and some hexdumping was how I came to understand the protocol. By the way this is the shoutcast protocol, painfully reverse-engineered by the icecast team. You may blame nullsoft for the lack of documentation. -Brendan --- >8 ---- List archives: http://www.xiph.org/archives/ icecast project homepage: http://www.icecast.org/ To unsubscribe from this list, send a message to 'icecast-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
Richard Fromm
2004-Aug-06 14:57 UTC
[icecast-dev] bug report w.r.t. streaming of metadata in icecast
On Fri, 10 Aug 2001, Brendan Cully wrote:> The server returns an icy-metaint header which tells where the info > will be inserted. If, say, it's 4096 then you'll find the metadata > after every 4096 bytes of MP3 data.that's what i originally thought was supposed to happen, which is why i sent the original mail with a bug report, saying i was expecting periodic insertion of metadata (icy-metaint was what i assumed indicated how often), but what was really happening was that the data got inserted once (or sometimes zero times, as per what you say and indeed sounds like an ices bug, not an icecast bug). i just want to clarify, though -- it does *not* get periodically inserted every 4096 bytes (in this instance), and that is the intention. it will get inserted once on some 4096 byte boundary, whenever a new client connects to the server. and it will get reinserted once for any new client. and it will also get reinserted whenever the source tells icecast to update the metadata, which is typically when it switches to a new song. yes? orry if i'm taking up so much e-mail on what once i understand it is i think a reasonably simple issue. - rich --- >8 ---- List archives: http://www.xiph.org/archives/ icecast project homepage: http://www.icecast.org/ To unsubscribe from this list, send a message to 'icecast-dev-request@xiph.org' containing only the word 'unsubscribe' in the body. No subject is needed. Unsubscribe messages sent to the list will be ignored/filtered.
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