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Christopher
Joined: 24 Feb 2011
Posts: 12
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 Posted: Sat Feb 21, 2015 7:58 pm Post subject: Streaming an MP2 file without reencoding? |
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I've been trying to stream an .MP2 file, using ezstream, expressly to avoid transcoding it using sox, darkice, ices2, lame, whatever.
Frustratingly ezstream bombs out when I load it:
ezstream: Streaming ``birdsong-trimmed'' (file: /usr/share/icecast/media/test.mp2)
ezstream: Exiting ...m00s]
I tried specifying the file directly in the XML and with an M3U but neither worked.
Sidenote: before the "Exiting" text, I saw what appeared to be reltime playback status, which would figure given the switches I was specifying, but it stuck at 0m00s before timing out.
I assumed it'd be able to handle MP2, is this not so? I've done loads of Googling and I know it'd be easy to transcode and stream, but I'm deliberately trying to live stream (not fileserve) bit-accurate to the original source.
Pipe dream or doable?
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dm8tbr
Joined: 09 Feb 2013
Posts: 45
Location: icecast.org
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| Posted: Mon Feb 23, 2015 3:50 pm Post subject: yuck |
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In theory MPEG 1 layer 2 (aka MP2) should also work with Icecast. After all we just forward the raw bitstream in case of "unsupported" formats (this includes MP3 and by extension MP2).
The challenge will be to find a player that plays this without barfing up its intestines.
I'm unsure, but maybe avconv/ffmpeg would work in such a setting, with the copy flag set on audio and the output set to Icecast mode.
TBH: It would probably be easier to just live encode it to Opus and at sufficient bitrate there should be no discernible quality loss. |
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Christopher
Joined: 24 Feb 2011
Posts: 12
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| Posted: Wed Feb 25, 2015 3:50 pm Post subject: |
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Ah, I'd never considered trying with ffmpeg! I'll give it a shot and see what happens.
Back when I used a Psion Wavefinder to listen to DAB, the DABBar third party control software had an integrated streaming server which exposed each PID as a .mp2 URL and streamed them live without transcoding. Winamp 2 handled it just fine, so I have high hopes for VLC and Foobar...
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dm8tbr
Joined: 09 Feb 2013
Posts: 45
Location: icecast.org
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| Posted: Wed Feb 25, 2015 4:08 pm Post subject: |
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VLC should work for sure.
It would happily play MPEG-TS with MPEG1L2 audio from my DBOX2 back in the days, also exposed as a (horribly unstable) HTTP stream. |
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Christopher
Joined: 24 Feb 2011
Posts: 12
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| Posted: Fri Feb 27, 2015 11:45 pm Post subject: |
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All manner of problems. Got avconv and ffmpeg just for comparison's sake (I'm aware the former is a fork of the latter) and set about trying to make it stream to my icecast 2.3.3 server.
I thought I was getting the formatting wrong... Now I'm just wondering if there's a massive undetected regression in the code.
Looks what happens when I try to stream the MP2 to stdout:
| Code: |
[me /dev] $ ffmpeg -c:a:0 mp2 -i /tmp/file.mp2 -
ffmpeg version N-70284-g0a23129 Copyright (c) 2000-2015 the FFmpeg developers
built with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-11)
configuration:
libavutil 54. 19.100 / 54. 19.100
libavcodec 56. 26.100 / 56. 26.100
libavformat 56. 23.106 / 56. 23.106
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 11.102 / 5. 11.102
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
[mp3 @ 0x1e470e0] Format mp3 detected only with low score of 1, misdetection possible!
[mp3 @ 0x1e470e0] Could not find codec parameters for stream 0 (Audio: mp2, 0 channels, s16p): unspecified frame size
Consider increasing the value for the 'analyzeduration' and 'probesize' options
/tmp/file.mp2: could not find codec parameters
Input #0, mp3, from '/tmp/file.mp2':
Duration: N/A, start: 0.000000, bitrate: N/A
Stream #0:0: Audio: mp2, 0 channels, s16p
[NULL @ 0x1e48680] Unable to find a suitable output format for 'pipe:'
pipe:: Invalid argument |
The same thing happens if I don't specify the input codec.
I'm really confused now.
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dm8tbr
Joined: 09 Feb 2013
Posts: 45
Location: icecast.org
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| Posted: Sat Feb 28, 2015 8:08 am Post subject: |
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Just tried this on my machine and it worked flawlessly:
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$ avconv -re -i sample-256kbps.mp2 -acodec copy -content_type audio/mpeg icecast://source:password@icecast.example.org:8000/test.mp2
avconv version 11.2-6:11.2-1, Copyright (c) 2000-2014 the Libav developers
[…] |
- -re sets it to real time reading, else it would run too fast
- -i sets the input file
- -acodec copy tells it not to touch the encoded data, but just pass it on
- -content_type audio/mpeg sends the right content type (required with newer Icecast!)
- icecast:// is the URL to stream to, including credentials
- In case your Icecast is older than 2.4, you'll need to pass the -legacy_icecast protocol option and live with some protocol limitations like lack of disconnection detection in avconv.
Conclusion:
As Icecast doesn't touch the stream in any way for legacy encodings, it just works.
Recent avconv works well in this context. |
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Christopher
Joined: 24 Feb 2011
Posts: 12
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| Posted: Sat Feb 28, 2015 11:46 am Post subject: |
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Oh, I wonder if it's because my avconv is 11_beta1 ... I thought I'd grabbed the most recent version.
When I tried your oneliner, I got:
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[christof ~] $ avconv -re -i /usr/share/icecast/media/birdsong-trimmed.mp2 -acodec copy -content_type audio/mpeg icecast://source:bluefox50qwe@localhost:8000/birdsong
avconv version 11_beta1, Copyright (c) 2000-2014 the Libav developers
built on Feb 27 2015 21:39:27 with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-11)
[mp3 @ 0x1fa7120] Format detected only with low score of 25, misdetection possible!
[mp3 @ 0x1fa7120] Could not find codec parameters (Audio: mp3, 0 channels, s16p)
[mp3 @ 0x1fa7120] Estimating duration from bitrate, this may be inaccurate
/usr/share/icecast/media/birdsong-trimmed.mp2: could not find codec parameters
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I upgraded to avconv 11.2, and it still gives me the same error. There's something odd going on. (It's a valid MP2, VLC has no problem playing or even copying the ES to a new MP2 which has the same filesize). Time to make some more MP2 test files!
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Christopher
Joined: 24 Feb 2011
Posts: 12
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| Posted: Sat Feb 28, 2015 12:19 pm Post subject: |
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Haha, so a new and interesting error this time. Encoded a test file with twolame from FLAC...
Ugpraded to Icecast 2.4.1. libavconv 11.2. CentOS 6.6 x64.
| Code: |
[christof /usr/share/icecast/media] $ avconv -re -i /usr/share/icecast/media/test2.mp2 -acodec copy -content_type audio/mpeg icecast://source:xxx@localhost:8000/birdsong
avconv version 11.2, Copyright (c) 2000-2014 the Libav developers
built on Feb 28 2015 11:59:48 with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-11)
[mp3 @ 0x3310120] max_analyze_duration 5000000 reached
[mp3 @ 0x3310120] Estimating duration from bitrate, this may be inaccurate
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, mp3, from '/usr/share/icecast/media/test2.mp2':
Metadata:
title : Ol' MacDonald
album : Boys Night Out
publisher : Capitol Records
genre : Vocal
Artistsort : Sinatra, Frank
track : 06/19
artist : Frank Sinatra
album_artist : The Rat Pack
ALBUMARTISTSORT : Rat Pack, The
date : 2004
Duration: 00:02:41.06, start: 0.000000, bitrate: 224 kb/s
Stream #0.0: Audio: mp2, 44100 Hz, 2 channels, s16p, 224 kb/s
Unable to find a suitable output format for 'icecast://source:xxx@localhost:8000/birdsong' |
Same error if I use the FQDN for the server.
Have you got a special magic version of libavconv? 
Forcing the MP2 format got me further, but it seemed initially to bomb immediately after starting to stream. But after that, it began to work, as long as I used the force format flag. Unfortunately though neither VLC nor Foobar begin to play the stream.
| Code: |
[christof /usr/share/icecast/media] $ avconv -re -i /usr/share/icecast/media/test2.mp2 -c:a copy -f mp2 -content_type audio/mpeg icecast://source:xxx@my.domain.tld:8000/birdsong
avconv version 11.2, Copyright (c) 2000-2014 the Libav developers
built on Feb 28 2015 11:59:48 with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-11)
[mp3 @ 0x16ee140] max_analyze_duration 5000000 reached
[mp3 @ 0x16ee140] Estimating duration from bitrate, this may be inaccurate
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, mp3, from '/usr/share/icecast/media/test2.mp2':
Metadata:
title : Ol' MacDonald
album : Boys Night Out
publisher : Capitol Records
genre : Vocal
Artistsort : Sinatra, Frank
track : 06/19
artist : Frank Sinatra
album_artist : The Rat Pack
ALBUMARTISTSORT : Rat Pack, The
date : 2004
Duration: 00:02:41.06, start: 0.000000, bitrate: 224 kb/s
Stream #0.0: Audio: mp2, 44100 Hz, 2 channels, s16p, 224 kb/s
Output #0, mp2, to 'icecast://source:xxx@my.domain.tld:8000/birdsong':
Metadata:
title : Ol' MacDonald
album : Boys Night Out
publisher : Capitol Records
genre : Vocal
Artistsort : Sinatra, Frank
track : 06/19
artist : Frank Sinatra
album_artist : The Rat Pack
ALBUMARTISTSORT : Rat Pack, The
date : 2004
encoder : Lavf56.1.0
Stream #0.0: Audio: mp2, 44100 Hz, stereo, 224 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Press ctrl-c to stop encoding
size= 1968kB time=71.99 bitrate= 223.9kbits/s |
VLC borks with the following:
| Quote: |
es debug: did not sync on first block
mpeg_audio debug: emulated startcode (no startcode on following frame) |
More investigation required.
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dm8tbr
Joined: 09 Feb 2013
Posts: 45
Location: icecast.org
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| Posted: Sat Feb 28, 2015 12:31 pm Post subject: |
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I suspect it's the output format guessing.
In general having a "file extension" on your mountpoint is useful as there are still many broken players out there.
The alternative is probably to force output format by adding "-f mp2" right before icecast://
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Christopher
Joined: 24 Feb 2011
Posts: 12
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| Posted: Sat Feb 28, 2015 1:11 pm Post subject: |
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Yep, did both, sadly still doesn't work. Been trying all sorts, even transcoding experimenting with bitstream filters, specifying timecode options, etc - just looks like this won't work.
Transcoded Opus it is! 
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