Problem when seeking with oggmux/vorbisenc

[Tiago Katcipis]

Hi,


On Thu, Feb 13, 2014 at 5:24 PM, Thiago Santos <thiago.sousa.santos@
collabora.com> wrote:

>  On 02/13/2014 02:16 PM, Tiago Katcipis wrote:
>
>     Hi,
>
>
> Oi,
>
>
>  I don't know if this is a problem or if I'm missing something. All I'm
> trying to do is to transcode audio, from any format (thanks to decodebin:-) to
> OGG/Vorbis. Just doing this for an entire file is pretty straightforward
> and the example code I'm providing already does that.
>
>  But when i try to extend it to seek to a specific position of the audio,
> and then transcoding, then i get some problems.
>
>  When i perform a non-flushing seek... the seek call hangs forever. If i
> perform a flushing seek everything goes "ok", but i end up with a messed
> up OGG file :-(.
>
>  When i transcode the entire file:
>
> ./ogg-seek-test <audio-src-file>
> file /tmp/test.ogg
> /tmp/test.ogg: Ogg data, Vorbis audio, mono, 8000 Hz, ~22400 bps, created
> by: Xiph.Org libVorbis I
>
> play /tmp/test.ogg
> /tmp/test.ogg:
>  File Size: 369k      Bit Rate: 23.4k
>   Encoding: Vorbis
>   Channels: 1 @ 16-bit
> Samplerate: 8000Hz
> Replaygain: off
>   Duration: 00:02:06.14
>
> When i try to seek, to transcode only a part of the file:
>
> ./ogg-seek-test <audio-src> 10
>
> file /tmp/test.ogg
> /tmp/test.ogg: Ogg data
>
> play /tmp/test.ogg
> play FAIL formats: can't open input file `/tmp/test.ogg': Input not an Ogg
> Vorbis audio stream
>
>  The source code is here:
> https://gitorious.org/katcipis
> -playground/playground/source/dfa5c8849e73ba15d15ea9dc11c1913d2685f5e0:c/
> gstreamer/oggmux-seek-test/ogg-seek-test.c
>
>
>  Any help is deeply appreciated.
>
>
> There was a bug in oggmux regarding proper flushing when handling a seek.
>
> Just got fixed with commit a6890ec7ef69f34b38ae2c600f136b43574102e7 in
> gst-plugins-base git master.
>

That is good news :-)


>
> Please report if it still doesn't work for you.
>

Ill check it out, sorry i didn't looked on the bug list, i really thought i
was making some mistake :-). But i have another question, since we are
talking about OGG/Vorbis.

I really need to use CBR on vorbisenc, but it don't matter how much i set
it to be on a fixed bitrate the bitrate is still variable. If i run "file"
on the ogg file it does says it has the right bitrate, but when i play it
with "play" it have another bitrate (always a little higher than the one
configured). Calculating the size manually also indicates the
bitrateinformed by play, so it seems that it is not respecting the
configured
bitrate.

For example i run:

gst-launch-1.0 pulsesrc ! audioconvert ! audioresample !
audio/x-raw,rate=8000,channels=1 ! vorbisenc managed=true min-bitrate=28000
bitrate=28000 max-bitrate=28000 ! oggmux ! filesink location=/tmp/test.ogg

I get:

file /tmp/test.ogg
/tmp/test.ogg: Ogg data, Vorbis audio, mono, 8000 Hz, <28000 ~28000 >28000
bps, created by: Xiph.Org libVorbis I

Its ok, but on play:
play /tmp/test.ogg
/tmp/test.ogg:
 File Size: 13.6k     Bit Rate: 35.9k

It seems that the bitrate cant be fixed, but i read that vorbis does
support CBR.

Thanks for the help,
Tiago Katcipis




>
> --
> Cheers,
> Thiago
>
>
>  Best regards,
> Tiago Katcipis
>
>
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