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Real, Winamp, WMP & On-demand File Streaming

 
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Anonymous
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PostPosted: Wed Nov 30, 2005 4:35 am    Post subject: Real, Winamp, WMP & On-demand File Streaming Reply with quote

What is going on between the player and the Icecast server that Real and Winamp support but Windows Media Player does not?

Initially, I thought the Icecast server merely supported http download of files and it was up to the player design whether it buffered play before download completed. Then somebody pointed out to me that Winamp streamed from his Icecast server even if Windows Media Player merely buffered play.

The key was to put the URL to the MP3 file via the Icecast server into a M3U playlist. Then I found that both Winamp and Real Player 10 could seek to any point in the file with download picking up from near the seek point. However, WMP cannot jump past the continuous-from-the-beginning download progress; I believe it supports server seeking only via Windows Media Server (IIS?).

I also found that a SMIL file pointing to the Icecast URL would allow Real Player to start with offset (Clip-begin="...s") and play for defined duration (dur="...s"). Thus, playlists more complex than M3U that were the domain of Realserver or Windows Media Server (SMIL, HTML + TIME, ASX) can be used to some extent with Icecast.

In these respects there is some functional equivalency between the Icecast server and the Real server. Heretofore, I had always thought that http 'streaming' was just a euphemism and that one had to use rtsp or mms for the support of seek. What is going on between the player and the Icecast server that Real and Winamp support but Windows Media Player does not?

Other differences:
Winamp got confused by a M3U playlist containing MP3, WAV and MP2; it would not allow jumping around in the playlist, relabelled the displayed WAV filename with the one above or below it; when closed, the winamp process and download continued and new instances of winanp would not display until the rogue one was stopped.

Real handled all 3 types gracefully and supported seeking in all. Oddly it showed the download progress for both MP3 and MP2 but not for WAV - even the style of the progress bar changed. Its download rate was 10-15 times faster than Winamp's - that may be a negative if one is seeking around a lot in one file, in which case, Windows Media Player's one-time download and buffered play would be easier on the network and server.

If you don't use a playlist file and link directly to the file on the Icecast server from the browser, then Windows Media Player's buffered play is a big advantage over the full download and then play that seems to be the way Winamp and Real behave.

If I have any of this wrong, please let me know! Otherwise, I hope it's of help to others.

Tom
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Anonymous
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PostPosted: Thu Dec 01, 2005 4:58 am    Post subject: Seeks within RA and WMA files Reply with quote

Real Player and Icecast also support seeking within Smile Real Audio (.ra) but not within Crying or Very sad Windows Media Audio (.wma) files. For the latter, the Real Player behaviour seems to be identical to Windows Media Player - a seek beyond the download progress snaps back to the play position.

Any chance that WMA seeks might become supported or is this strictly a player question?

Tom
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karlH
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PostPosted: Thu Dec 01, 2005 4:30 pm    Post subject: Reply with quote

WMA is not supported, so while you can download a WMA file via icecast, it doesn't do the required processing of WMA to allow for proper seeking. The problem is purely format parsing.

karl.
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Anonymous
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PostPosted: Thu Dec 01, 2005 7:00 pm    Post subject: Reply with quote

Where is there a list of file types for which Icecast supports file parsing or seeking within the file?

Tom
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karlH
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PostPosted: Thu Dec 01, 2005 8:40 pm    Post subject: Reply with quote

There isn't, it's not something that icecast is written for. The file serving engine has seeking at a simple level, so formats like mp3 etc are probably ok, but other files have codec setup type information which need to be parsed, and presented to the listener before the real seek point. I can see that being done for Ogg possibly but WMA is unlikely to happen.

karl.
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Anonymous
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PostPosted: Fri Dec 02, 2005 1:48 am    Post subject: My List of Icecast Seekable File Types Reply with quote

In the absence of an official list of file types for which Icecast 2.3.0 supports file parsing or seeking within the file for http served file play-on-demand, here's my unofficial, empirically developed list:

Officially Supported:
    MP3
    Ogg Vorbis

Apparently Allowed:
    MP2
    RA
    WAV

Apparently Unsupported:
    WMA


If you have any other experience to add, maybe we can maintain and grow the list.

Tom
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Anonymous
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PostPosted: Fri Dec 02, 2005 2:23 am    Post subject: Reply with quote

karlH wrote:
I can see that being done for Ogg possibly but WMA is unlikely to happen.

WMA is in the 'certainly nice to have' category given its widespread popularity and superior quality low bitrate audio coding. But I wonder if it's the player not issuing the commands that the server needs for a seek to happen. Real Player for Windows may be using the Windows Media Player core for WMA and merely dresses it in the Real Player cloak - if WMP does not support http file seeking/parsing/streaming for WMA or any file types, then it would follow that RealPlayer might not either for WMA.

Tom
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karlH
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PostPosted: Fri Dec 02, 2005 3:01 am    Post subject: Reply with quote

Strickly speaking, for streaming, we only really support Ogg and a generic passthrough mechanism. The passthrough mechanism allows for mp3[pro], nsv. aac*, (and whatever formats that don't need manipulating). For on-demand files, we handle the request for partial transfers but the files are not modified before being sent to the listener, so in cases like mp3 and aac, due to the layout of the files, playback can resume quickly, but in others it won't

To some, icecast handling WMA would be great, but the Xiph Foundation has been setup to help promote free and open media, WMA would require specific handling (my understanding is that the pro version is completely different format as well), so there is no incentive for us to add it.

Most people would argue the 'superior quality low bitrate audio coding' expecially with the aoTuV b4.x showing up very well in listening tests. As for how WMP handles seeking, I can't say as I don't have it.

karl
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PostPosted: Wed Mar 29, 2006 7:42 pm    Post subject: Reply with quote

karlH wrote:

For on-demand files, we handle the request for partial transfers but the files are not modified before being sent to the listener, so in cases like mp3 and aac, due to the layout of the files, playback can resume quickly, but in others it won't
karl


Ok. I understood, that OGG files are best for seeking at Icecast or web server ?
My http server (Linux+Apache) great serve mp3 files with full seeking support (if I click the m3u playlist with http url), but why if m3u is pointing at url of .ogg file (at the same apache and the same folder), seeking in the Winamp (I tried with older and newer, including 5.12) is not available ?

Is it player's fault ? I tried to play in Foobar2k but it is not seeking at all "on demand" programme (ogg, but mp3 too).

Or it is my mistake with configuration at server side ?
It would work at apache server http or Icecast server http (I know, that Icecast has the "webroot" directory, with that it deals http service too).

Could You explain me, where is the solution ?
Thanks a lot !
Rob.
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