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diff --git a/src/ms_adpcm.c b/src/ms_adpcm.c
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index 5e8f1a31..a21cb994 100644
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--- a/src/ms_adpcm.c
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+++ b/src/ms_adpcm.c
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@@ -128,8 +128,14 @@ wavlike_msadpcm_init	(SF_PRIVATE *psf, int blockalign, int samplesperblock)
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 	if (psf->file.mode == SFM_WRITE)
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 		samplesperblock = 2 + 2 * (blockalign - 7 * psf->sf.channels) / psf->sf.channels ;
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-	if (blockalign < 7 * psf->sf.channels)
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-	{	psf_log_printf (psf, "*** Error blockalign (%d) should be > %d.\n", blockalign, 7 * psf->sf.channels) ;
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+	/* There's 7 samples per channel in the preamble of each block */
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+	if (samplesperblock < 7 * psf->sf.channels)
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+	{	psf_log_printf (psf, "*** Error samplesperblock (%d) should be >= %d.\n", samplesperblock, 7 * psf->sf.channels) ;
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+		return SFE_INTERNAL ;
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+		} ;
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+
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+	if (2 * blockalign < samplesperblock * psf->sf.channels)
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+	{	psf_log_printf (psf, "*** Error blockalign (%d) should be >= %d.\n", blockalign, samplesperblock * psf->sf.channels / 2) ;
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 		return SFE_INTERNAL ;
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 		} ;
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