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penetrode
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Joined: 29 Dec 2003
Posts: 244
Location: Calgary, Alberta

PostPosted: Thu Mar 07, 2013 2:33 am    Post subject: Capturing flash audio streams Reply with quote

My public broadcaster (the CBC) provides radio programming online in the form of podcasts. At the same time, broadcasts may be streamed for up to three months after the broadcast date. Strangely, though a given program might be available as a podcast, sometimes parts of it are missing from the podcast and only available in the stream.

In the past, I captured these streams using mplayer, but a couple of years ago CBC switched to Flash-based publishing. An examination of the player source code reveals that the rtmp URL is obfuscated.

Is there a simple way of getting around this so that I can capture streams again and listen to them when off-network?

For an example, have a look at http://www.cbc.ca/asithappens/episode/2013/02/27/wednesday-alison-redford-italian-election-greg-gatenby/# and click on the "Listen" link. This opens the CBC Flash audio player with a playlist.
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syn0ptik
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Joined: 09 Jan 2013
Posts: 208

PostPosted: Thu Mar 07, 2013 10:16 am    Post subject: Reply with quote

you could sniff with tcpdump and investigate what link used for playing audio.
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curmudgeon
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PostPosted: Sat Mar 09, 2013 2:53 am    Post subject: Reply with quote

Using tcpdump is mandatory for things like this (and in this case, it reveals you have might have made some incorrect assumptions :) ).

Capturing rtmp media is a pain (and not always reliable), but in this case, I only see simple http.

Start the player after running this command:

Code:

# tcpdump -A -s 0 > dump.text


After the audio starts, kill tcpdump, and look through the file (this takes experience to do efficiently, but in general look for GET commands and media filetypes):

This looks promising:

Code:

GET /maven_legacy/thumbnails/15/1/asithappens_20130227_92577_uploaded.mp3 HTTP/1.1
User-Agent: Opera/9.80 (X11; Linux x86_64) Presto/2.12.388 Version/12.13
Host: thumbnails.cbc.ca
Accept: text/html, application/xml;q=0.9, application/xhtml+xml, image/png, image/webp, image/jpeg, image/gif, image/x-xbitmap, */*;q=0.1
Accept-Language: en,en-US;q=0.9
Accept-Encoding: gzip, deflate
Connection: Keep-Alive
DNT: 1


So:

Code:

$ wget -S -c 'http://thumbnails.cbc.ca/maven_legacy/thumbnails/15/1/asithappens_20130227_92577_uploaded.mp3'
--2013-03-09 02:33:13--  http://thumbnails.cbc.ca/maven_legacy/thumbnails/15/1/asithappens_20130227_92577_uploaded.mp3
Resolving thumbnails.cbc.ca... 119.224.129.208, 119.224.129.210
Connecting to thumbnails.cbc.ca|119.224.129.208|:80... connected.
HTTP request sent, awaiting response...
  HTTP/1.1 200 OK
  Server: Apache
  ETag: "0b0806e3e5d3f31d67e0be49183fff5e:1362009216"
  Last-Modified: Wed, 27 Feb 2013 23:53:36 GMT
  Accept-Ranges: bytes
  Content-Length: 24581015
  Content-Type: audio/mpeg
  Date: Sat, 09 Mar 2013 02:33:14 GMT
  Connection: keep-alive
Length: 24581015 (23M) [audio/mpeg]
Saving to: ‘asithappens_20130227_92577_uploaded.mp3’

100%[==========================================================================================================================================>] 24,581,015   160KB/s   in 2m 11s

2013-03-09 02:35:25 (184 KB/s) - ‘asithappens_20130227_92577_uploaded.mp3’ saved [24581015/24581015]


I believe that is what you want (the file has the full 25:36 that the player shows as the length).
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