November 2009 - FFmpeg-soc - lists.ffmpeg.org

[PATCH]aacsbr: internal sample rate
by Alex Converse 27 Nov '09

27 Nov '09

Fs_SBR as defined by the specification is the SBR internal sample rate and defined to be twice the core coder nominal sample rate (listed in Table 4.82 - Sampling Frequency Mapping). ExtensionSamplingFrequency is the SBR output sample rate. The code currently uses ExtensionSamplingFrequency instead of Fs_SBR. This patch creates a new context variable to hold Fs_SBR. Caveats: *This doesn't support sample rates that are not nominal sample rates, however AFAIK FFmpeg's LC/Main decoder does not support them either. There are no official LC/Main test vectors for them. *This probably doesn't handle the 7350 Hz sample rate properly as 7350 is not listed in the table so presumably the nominal sample rate is 8000. FFmpeg does support AAC @ 7350 Hz. There are no official LC/Main test vectors for it, however I hacked one up. MPEG seems to have zero interest in this sample rate outside of scalable profiles, however it still appears to be legal in the mainstream profiles. [1] Ref: [1] http://lists.mpegif.org/pipermail/mp4-tech/2009-February/008661.html http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2009-February/061946.html

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[soc]: r5465 - aac-sbr/aacsbr.c
by alexc 27 Nov '09

27 Nov '09

Author: alexc Date: Fri Nov 27 03:22:19 2009 New Revision: 5465 Log: k2 is calculated using the first bs_stop_freq entries of the *sorted* vector stopDk. Modified: aac-sbr/aacsbr.c Modified: aac-sbr/aacsbr.c ============================================================================== --- aac-sbr/aacsbr.c Fri Nov 27 00:32:56 2009 (r5464) +++ aac-sbr/aacsbr.c Fri Nov 27 03:22:19 2009 (r5465) @@ -146,6 +146,7 @@ static int sbr_make_f_master(AACContext unsigned int start_min, stop_min; int k; const uint8_t *sbr_offset_ptr; + int stop_dk[13]; if (ac->m4ac.ext_sample_rate < 32000) { temp = 3000; @@ -179,10 +180,13 @@ static int sbr_make_f_master(AACContext if (spectrum->bs_stop_freq < 14) { sbr->k[2] = stop_min; - for (k = 0; k < spectrum->bs_stop_freq; k++) { - sbr->k[2] += lroundf(stop_min * powf(64.0f / (float)stop_min, (k + 1) / 13.0f)) - + for (k = 0; k < 13; k++) { + stop_dk[k] = lroundf(stop_min * powf(64.0f / (float)stop_min, (k + 1) / 13.0f)) - lroundf(stop_min * powf(64.0f / (float)stop_min, k / 13.0f)); } + qsort(stop_dk, 13, sizeof(stop_dk[0]), qsort_comparison_function); + for (k = 0; k < spectrum->bs_stop_freq; k++) + sbr->k[2] += stop_dk[k]; } else if (spectrum->bs_stop_freq == 14) { sbr->k[2] = 2*sbr->k[0]; } else if (spectrum->bs_stop_freq == 15) {

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[soc]: r5464 - aac-sbr/aacsbr.c
by alexc 27 Nov '09

27 Nov '09

Author: alexc Date: Fri Nov 27 00:32:56 2009 New Revision: 5464 Log: Fix the logic on the inner loop in sbr_hf_calc_npatches. The loop must always be entered at least once. The condition listed in the specification is the exit condition and thus must be inverted. Modified: aac-sbr/aacsbr.c Modified: aac-sbr/aacsbr.c ============================================================================== --- aac-sbr/aacsbr.c Fri Nov 27 00:32:55 2009 (r5463) +++ aac-sbr/aacsbr.c Fri Nov 27 00:32:56 2009 (r5464) @@ -356,7 +356,7 @@ static int sbr_hf_calc_npatches(AACConte do { int odd = 0; - for (i = k; sb <= (sbr->k[0] - 1 + msb - odd); i--) { + for (i = k; i == k || sb > (sbr->k[0] - 1 + msb - odd); i--) { sb = sbr->f_master[i]; odd = (sb - 2 + sbr->k[0]) & 1; }

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[soc]: r5463 - aac-sbr/aacsbr.c
by alexc 27 Nov '09

27 Nov '09

Author: alexc Date: Fri Nov 27 00:32:55 2009 New Revision: 5463 Log: Remove a superfluous increment. k should be set to the first index of f_master that is >= goal_sb. The final increment of the loop where the condition fails takes care of that. Modified: aac-sbr/aacsbr.c Modified: aac-sbr/aacsbr.c ============================================================================== --- aac-sbr/aacsbr.c Thu Nov 26 22:52:59 2009 (r5462) +++ aac-sbr/aacsbr.c Fri Nov 27 00:32:55 2009 (r5463) @@ -351,7 +351,6 @@ static int sbr_hf_calc_npatches(AACConte if (goal_sb < sbr->k[3] + sbr->m) { for (k = 0; sbr->f_master[k] < goal_sb; k++); - k++; } else k = sbr->n_master;

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[PATCH 2/2]aacsbr: Change vk0 and vk1 to int16_t to prevent a size mismatch on memcpy.
by Alex Converse 26 Nov '09

26 Nov '09

Required to fix al_sbr_e_32_1.mp4

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[PATCH 1/2]aacsbr: Allocate vk0 and vk1 on the stack to prevent memory leaks.
by Alex Converse 26 Nov '09

26 Nov '09

There are returns all over this code. The size was taken from f_master. Required to fix al_sbr_e_32_1.mp4

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[PATCH]aacsbr: Pass current spectrum_params to sbr_make_f_master.
by Alex Converse 26 Nov '09

26 Nov '09

Currently we are passing spectrum parameters from the previous frame to sbr_make_f_master. Required to fix al_sbr_e_32_1.mp4

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[PATCH]aacsbr: Set ext_sample_rate for implicit SBR
by Alex Converse 26 Nov '09

26 Nov '09

This fixes al_sbr_e_44_1.mp4. Alternatively we could set it in the AudioSpecificConfig *AND* ADTS code.

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[PATCH]aacsbr: Read SBR bits from a second GetBitContext to prevent unrecoverable over-reads and get automatic under-read protection.
by Alex Converse 26 Nov '09

26 Nov '09

Comments on alternate approaches are welcome.

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[PATCH]aacsbr: If SBR's reset procedure fails switch back to pure upsampling mode.
by Alex Converse 26 Nov '09

26 Nov '09

If SBR reset fails, something very bad(tm) has happened and we should wait for the next header.

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