#2686: Native AAC encoder collapses at high bitrates on some samples
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Reporter: Kamedo2 | Owner:
Type: defect | Status: open
Priority: normal | Component: avcodec
Version: git-master | Resolution:
Keywords: aac | Blocked By:
regression | Reproduced by developer: 1
Blocking: |
Analyzed by developer: 0 |
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Comment (by Kamedo2):
Isn't line 334 of libavcodec/aacpsy.c:
{{{
for (g = 0; g < ctx->num_bands[j]-1; g++) {
AacPsyCoeffs *coeff = &coeffs[g];
float bark_width = coeffs[g+1].barks - coeffs->barks;
coeff->spread_low[0] = pow(10.0, -bark_width *
PSY_3GPP_THR_SPREAD_LOW);
coeff->spread_hi [0] = pow(10.0, -bark_width *
PSY_3GPP_THR_SPREAD_HI);
coeff->spread_low[1] = pow(10.0, -bark_width * en_spread_low);
coeff->spread_hi [1] = pow(10.0, -bark_width * en_spread_hi);
pe_min = bark_pe * bark_width;
minsnr = exp2(pe_min / band_sizes[g]) - 1.5f;
coeff->min_snr = av_clipf(1.0f / minsnr, PSY_SNR_25DB,
PSY_SNR_1DB);
}
}}}
strange? I doubt the sanity of lower spreading function at the highest
band, because using -cutoff 18000 option improves the quality on
problematic samples, and these problematic samples always includes strong
20-22kHz sounds. (The default cutoff is 18k at 192kbps, 20k at 256kbps,
and 22k at 320kbps.)
--
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2686#comment:31>
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