#37 improve audio quality

closed
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5
2007-04-21
2007-02-14
Karol Krenski
No

Hi,

I am the author of a couple of Inkscape movies:
http://www.inf.sgsp.edu.pl/lab/filmiki/filmiki.php

Those were recorded with gvidcap. The CPU didn't look quite busy (I noticed having X in Vesa mode is better than running under nv or nvidia, nvidia was too heavy for the CPU, strange...)

I am not happy with audio quality. Many audio frames were lost. I would understand if CPU load was 90%, but it was about 30% only.

I even tried to record the sound separately in another app. Quality was perfect, file a bit larger, except the combinated video+audio went out of sync pretty early :(

Any hope for audio quality improvement?

regards,
Karol

Discussion

  • Logged In: YES
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    must admit I haven't focussed on audio quality very much, yet, so there may be room for improvement code-wise.
    Still, have you tried the obvious things as per FAQ?
    The thing is: Even if you may think that since you're losing audio frames increasing the sample rate may not help, it actually could, because the audio frame drop may be the result of the attempt to keep a/v sync and higher audio sample/bit rates may make the atoms of audio data dumped smaller.

     
  • Karol Krenski
    Karol Krenski
    2007-02-14

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    >Still, have you tried the obvious things as per FAQ?
    There's not much on the FAQ page. The hacker attack, remember? ;)

    >increasing the sample rate
    [mp2 @ 0xb74dab10]Sampling rate 27088 is not allowed in mp2
    xtoffmpeg.c add_audio_stream(): Error while opening codec for output stream

    What are the rules/equation to find available sampling rates? The 27088 was just a random number I typed.

     
  • Karol Krenski
    Karol Krenski
    2007-02-14

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    The forum was auto-set to Polish and it works totally different than when it's set to English. Now I can see audio posts. Yes, better rates improve the quality, but now quality mysteriously became better with the default settings also. I will probably find out more when I record new movies.

     
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    and I should add that gvidcap is rather dated by now ... you should try 1.1.4p1 (or up if you are more daring)

     
    • status: open --> pending
     
  • Logged In: YES
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    no news from the original poster

     
  • Karol Krenski
    Karol Krenski
    2007-04-20

    • status: pending --> open
     
  • Karol Krenski
    Karol Krenski
    2007-04-20

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    The Linux distro I use ships a broken version of xvidcap (doesn't dump to a movie, only to separate images). I am waiting for a fix, that is being worked on. But as I commented before your suggestions (44100/64000) seem to resolve the issue.

     
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    alright then.
    1.1.5 has a hint in the manual.
    1.1.5+ will have the higher settins as the default and leave it to the user to optimize for size.

     
    • assigned_to: nobody --> charly4711
    • status: open --> closed
     
  • Karol Krenski
    Karol Krenski
    2007-04-21

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    > 1.1.5+ will have the higher settins as the default

    Seems reasonable. Audio was the main problem in xvidcap. As I also noticed in initial post VESA vs nv vs nvidia behaviour is strange. I suggest hinting that VESA may have superior performance, unless it's already in the docs.

     
  • Logged In: YES
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    hmm, not sure about that. I have zero problems with nvidia drivers. To the contrary, I've had reports where people solved their performance issues by fixing their nvidia config. They were only getting 2 or 3 fps at first and then got acceptable rates with a proper config.