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Thread: How to transrate mp3 stream to lower rate Apple iOS stream?

  1. #1
    Join Date
    Sep 2012
    Posts
    5

    Default How to transrate mp3 stream to lower rate Apple iOS stream?

    Hi, every expert:

    I am working on transrate a mp3 audio-only stream, say http://139.210.35.125:8111/channel0, which is 128kbps stream, to a m3u8 stream with lower than 40kbps bitrate.

    I configured the Wowza Media Server according to http://www.wowza.com/forums/content....UTcast-Icecast and
    http://www.wowza.com/forums/content....wza-Transcoder.

    I created a file as [install-dir]/content/ccradio_channel0.stream, which contains text "http://139.210.35.125:8111/channel0".

    When I configured Application.xml by not setting "transcoder" in Transcoder/LiveStreamTranscoder, I can get the transcoded stream from the url:
    http://10.16.32.213:1935/live/ccradi.../playlist.m3u8

    While when I tried to add "transcoder" for Transcoder/LiveStreamTranscoder in Application.xml and used an translate.xml template in http://www.wowza.com/forums/content....wza-Transcoder, the stream failed to be generated.
    The log error showed "the stream cannot be found".

    Anybody could tell me how to address this issue?
    Thanks a lot in advance!

    Xiaomeng Li

  2. #2

    Default

    Hi Xiaomeng,

    See the Transcoder Overview for supported decoding and encoding formats.

    You'll have to transcode to AAC to lower the bitrate.

  3. #3
    Join Date
    Sep 2012
    Posts
    5

    Default

    Randall:

    Sincerely thank you for quick reply.

    Do you mean I should use transcode instead of transrate?

    Below is my transrate.xml, should I add Decode section for with mp3 input?

    <Root>
    	<Transcode>
    		<Encodes>			
    			<!-- Setup for transrate MP3 stream for 3G mobile devices such as iOS, Android -->
    			<Encode>
    				<Enable>true</Enable>
    				<Name>aac</Name>
    				<StreamName>mp4:${SourceStreamName}_aac</StreamName>
    				<Video>
    					<!-- H.264, Disable-->
    					<Codec>Disable</Codec>
    					<Parameters>
    					</Parameters>
    				</Video>
    				<Audio>
    					<!-- AAC -->
    					<Codec>AAC</Codec>
    					<Bitrate>48000</Bitrate>
    				</Audio>
    				<Properties>
    				</Properties>
    			</Encode>
    		</Encodes>
    		<Decode>
    		</Decode>
    		<StreamNameGroups>
    		</StreamNameGroups>
    		<Properties>
    		</Properties>
    	</Transcode>
    </Root>

  4. #4

    Default

    You will need to transcode and transrate.

    I suggest using the stock audioonly.xml template and only changing the VideoCodec to Disable. I would not add or remove xml elements unless needed.

  5. #5
    Join Date
    Sep 2012
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    5

    Default

    Randall:

    Many thanks for your help!

    As you suggested, I am using audioonly.xml to transcode incoming mp3 stream into AAC stream.

    But I am not sure if the transcode really changes the bitrate to 48kbps as I set, so I am now finding a bitrate calculating tool to verify the result.

    Thanks!
    --Xiaomeng

  6. #6
    Join Date
    Sep 2012
    Posts
    5

    Default

    I am facing another issue, looks like the output stream is not a smooth network stream and has lots of bursts.

    I am wondering if WOWZA could smooth the transcoded stream?

    Thanks!
    --xiaomeng

  7. #7
    Join Date
    Dec 2007
    Posts
    21,962

    Default

    It could be a bitrate problem, too high for the bandwidth at the client.

    It could be an encoding problem.

    It could be a recording problem. If you are recording by making the StreamType "live-record", that will record each stream, which might be too much for your disk configuration. Try LiveStreamRecord to record just one, or add disks to a RAID 0 disk array.

    Richard

  8. #8
    Join Date
    Sep 2012
    Posts
    5

    Default

    rrlanham:

    Thanks for the answers!

    I did not use recording option, so it should not be a recording problem.

    Also I compared the network output for both input mp3 stream and output AAC stream, the input stream is much smoother than the output stream.
    So I believe that the transcoder may have problem, the transcode process may generate bursts of bitrate.


    Thanks!
    --Xiaomeng
    Last edited by xmli933; 09-12-2012 at 06:32 PM.

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