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IEEE 754 Float ACM codec (ID 3) n/a in Windows 7 64-bit?
LigH
post Apr 6 2014, 13:16
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No big surprise that Microsoft is going to make "Video for Windows" and the installable codec APIs ICM and ACM obsolete step by step. Even DirectShow is not favourable anymore, according to the plans of Microsoft. There are just too many tools available to cut off the support completely...

But one limitation became apparent recently when another user of our video forum tried to load a 32-bit float WAV using the AviSynth core function WavSource(), which seems to use VfW based A/V functions. It failed on a 64-bit Windows 7. Reported error reason: "Codec not installed."

I am not sure if uncompressed IEEE Float samples (IANA codec ID: 0x0003) need an explicit "codec" at all. I believe the "Microsoft Wave Mapper" was responsible for raw sample format conversions. But this seems to be absent in a 64-bit Windows 7.

It was not easy to check this issue at all. Windows XP used to enumerate ACM codecs in its Sound CPL, and among the Audio hardware drivers in the Device Manager. Windows 7 hides that part. GSpot 2.70a was able to "List Codecs and Other Filters", ald listed several ACM codecs, just not for codec ID 0x0003.

Is there any installable ACM codec for this format? Do any of the multi decoders register as responsible? I have ffdshow installed, and GSpot reports ff_acm.dll responsible for format 0x3313, but that doesn't help here.

There are other people who report to be able to load WAV files with float samples. But I am not sure if they have a 32 bit Windows or have another ACM installed (maybe based on A/V or capturing software); awaiting their detailed reply...


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nu774
post Apr 7 2014, 10:00
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In my environment (windows 7 64bit):
WAVEFORMATEXTENSIBLE header + CodecID 00001000-0000-0300-8000-00AA00389B71: success
WAVEFORMATEX header + CodecID 3: fail

Microsoft says that wave file having more than 16bit or 2 channels has to use WAVEFORMATEXTENSIBLE anyway.
http://msdn.microsoft.com/en-us/library/wi...3(v=vs.85).aspx
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LigH
post Apr 7 2014, 10:22
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I don't read that "can use" as "mandatory"; but possibly good to know that some functions do.


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nu774
post Apr 7 2014, 11:26
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QUOTE (LigH @ Apr 7 2014, 18:22) *
I don't read that "can use" as "mandatory"

Ah, you're right. tongue.gif
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LigH
post Apr 7 2014, 12:00
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Conclusion: Support for anything beyond stereo 16 bit integer PCM via legacy functions is not reliable, therefore AviSynth users shall better rely on 3rd party plugins with more flexible WAV support.


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LigH
post Apr 7 2014, 19:32
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In Windows XP SP3, AviSynth can open all the here contained scripts; the WAV files were created with Audacity 2.0.5, exporting to other uncompressed formats, selecting "WAV (Microsoft)" or "WAVEX (Microsoft)" respectively. I'll check tomorrow what Windows 7 does...


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LigH
post Apr 8 2014, 07:25
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Under Windows 7 SP1 64-bit, AviSynth opens 16 bit integer in both variants, but 32 bit float only with extensible header, with simple header it fails.

I was told that it works when AC3Filter is installed. But I could not confirm that claim. Even after installing the full version including an ACM codec, AviSynth still fails to open the float WAV file with simple header.

This post has been edited by LigH: Apr 8 2014, 07:32


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