Reconstructing AAC CPE - Revision history

Mkhodor: revert vandalism by TbpS51

2007-04-11T14:54:40Z

revert vandalism by TbpS51

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TbpS51 at 14:52, 11 April 2007

2007-04-11T14:52:53Z

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Multimedia Mike: revert spam/vandalism

2006-03-24T19:03:36Z

revert spam/vandalism

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70.33.25.195: "

2006-03-24T05:00:29Z

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Multimedia Mike: /* ms_decode(ic_stream ics1, ic_stream ics2, real spec_coeff1[1024], real spec_coeff2[1024]) */ two not to

2006-03-13T14:34:00Z

ms_decode(ic_stream ics1, ic_stream ics2, real spec_coeff1[1024], real spec_coeff2[1024]): two not to

← Older revision		Revision as of 07:34, 13 March 2006
Line 235:		Line 235:

	== ms_decode(ic_stream ics1, ic_stream ics2, real spec_coeff1[1024], real spec_coeff2[1024]) ==		== ms_decode(ic_stream ics1, ic_stream ics2, real spec_coeff1[1024], real spec_coeff2[1024]) ==
	This function decodes mid/side coding between to channels.		This function decodes mid/side coding between two channels.
	group = 0		group = 0
	nshort = frame_length / 8 (frame_length is usualy 1024)		nshort = frame_length / 8 (frame_length is usualy 1024)

Multimedia Mike: /* ifilter_bank() */

2006-03-13T07:08:04Z

ifilter_bank()

← Older revision		Revision as of 00:08, 13 March 2006
Line 287:		Line 287:

	== ifilter_bank() ==		== ifilter_bank() ==
			This function transforms the spectral data through a modified discrete cosine transform (MDCT) and windows the transformed time domain samples.

	== imdct_long() ==		== imdct_long() ==

Multimedia Mike: /* is_decode(ic_stream ics1, ic_stream ics2, real spec_coeff1[1024], real spec_coeff2[1024]) */

2006-03-13T07:06:17Z

is_decode(ic_stream ics1, ic_stream ics2, real spec_coeff1[1024], real spec_coeff2[1024])

← Older revision		Revision as of 00:06, 13 March 2006
Line 254:		Line 254:

	== is_decode(ic_stream ics1, ic_stream ics2, real spec_coeff1[1024], real spec_coeff2[1024]) ==		== is_decode(ic_stream ics1, ic_stream ics2, real spec_coeff1[1024], real spec_coeff2[1024]) ==
	This function decodes intensity stereo ~~decoding~~.		This function decodes intensity stereo coding.
	nshort = frame_length / 8 (frame_length is usually 1024)		nshort = frame_length / 8 (frame_length is usually 1024)
	group = 0		group = 0

Multimedia Mike: /* apply_scalefactors(ic_string ics, real spec_coeff[1024]) */ edit got stepped on

2006-03-13T06:29:23Z

apply_scalefactors(ic_string ics, real spec_coeff[1024]): edit got stepped on

← Older revision		Revision as of 23:29, 12 March 2006
Line 72:		Line 72:
	top = ics.section_scalefactor_band_offset[g][scalefactor_band + 1]		top = ics.section_scalefactor_band_offset[g][scalefactor_band + 1]
	if (ics.scalefactors[g][scalefactor_band] < 0) OR (ics.scalefactors[g][scalefactor_band] > 255)		if (ics.scalefactors[g][scalefactor_band] < 0) OR (ics.scalefactors[g][scalefactor_band] > 255)
	~~exponent~~ = ~~fraction = 0~~		scale = 1
	else		else
	exponent = ics.scalefactors[g][scalefactor_band] ~~>> 2~~		exponent = (ics.scalefactors[g][scalefactor_band] - 100) / 4.0
	~~fraction~~ = ~~ics.scalefactors[g][scalefactor_band] & 3~~		scale = 2<sup>exponent</sup>
	while (k < top)		while (k < top)
	spec_coeff[k + (groups * nshort) + 0] *= ~~pow2sf_tab[exponent]~~		spec_coeff[k + (groups * nshort) + 0] *= scale
	~~spec_coeff[k + (groups * nshort) + 0] *= pow2_table[fraction]~~		spec_coeff[k + (groups * nshort) + 1] *= scale
	~~spec_coeff[k + (groups * nshort) + 1] *= pow2sf_tab[exponent]~~		spec_coeff[k + (groups * nshort) + 2] *= scale
	spec_coeff[k + (groups * nshort) + 1] *= ~~pow2_table[fraction]~~		spec_coeff[k + (groups * nshort) + 3] *= scale
	spec_coeff[k + (groups * nshort) + 2] *= ~~pow2sf_tab[exponent]~~
	~~spec_coeff[k + (groups * nshort) + 2] *= pow2_table[fraction]~~
	spec_coeff[k + (groups * nshort) + 3] *= ~~pow2sf_tab[exponent]~~
	~~spec_coeff[k + (groups * nshort) + 3] *= pow2_table[fraction]~~
	k += 4		k += 4
	groups += ics.window_group_length[g]		groups += ics.window_group_length[g]
	~~pow2sf_tab[] is defined as:~~
	~~foreach i in -25..38~~
	~~pow2sf_tab[i] = 2<sup>i</sup>~~
	~~pow2_table[] is defined as:~~
	~~foreach i in 0..3~~
	~~pow2_table[i] = 2<sup>i/4</sup>~~

	== quant_to_spec(ic_stream ics, real spec_coeff[1024]) ==		== quant_to_spec(ic_stream ics, real spec_coeff[1024]) ==

Multimedia Mike: /* tns_decode_frame() */ basic algorithm assuming no tns data

2006-03-13T05:59:58Z

tns_decode_frame(): basic algorithm assuming no tns data

← Older revision		Revision as of 22:59, 12 March 2006
Line 72:		Line 72:
	top = ics.section_scalefactor_band_offset[g][scalefactor_band + 1]		top = ics.section_scalefactor_band_offset[g][scalefactor_band + 1]
	if (ics.scalefactors[g][scalefactor_band] < 0) OR (ics.scalefactors[g][scalefactor_band] > 255)		if (ics.scalefactors[g][scalefactor_band] < 0) OR (ics.scalefactors[g][scalefactor_band] > 255)
	~~scale~~ = 1		exponent = fraction = 0
	else		else
	exponent = (ics.scalefactors[g][scalefactor_band] ~~- 100) / 4.0~~		exponent = ics.scalefactors[g][scalefactor_band] >> 2
	~~scale~~ = ~~2<sup>exponent</sup>~~		fraction = ics.scalefactors[g][scalefactor_band] & 3
	while (k < top)		while (k < top)
	spec_coeff[k + (groups * nshort) + 0] *= ~~scale~~		spec_coeff[k + (groups * nshort) + 0] *= pow2sf_tab[exponent]
	spec_coeff[k + (groups * nshort) + 1] *= ~~scale~~		spec_coeff[k + (groups * nshort) + 0] *= pow2_table[fraction]
	spec_coeff[k + (groups * nshort) + 2] *= ~~scale~~		spec_coeff[k + (groups * nshort) + 1] *= pow2sf_tab[exponent]
	spec_coeff[k + (groups * nshort) + 3] *= ~~scale~~		spec_coeff[k + (groups * nshort) + 1] *= pow2_table[fraction]
			spec_coeff[k + (groups * nshort) + 2] *= pow2sf_tab[exponent]
			spec_coeff[k + (groups * nshort) + 2] *= pow2_table[fraction]
			spec_coeff[k + (groups * nshort) + 3] *= pow2sf_tab[exponent]
			spec_coeff[k + (groups * nshort) + 3] *= pow2_table[fraction]
	k += 4		k += 4
	groups += ics.window_group_length[g]		groups += ics.window_group_length[g]
			pow2sf_tab[] is defined as:
			foreach i in -25..38
			pow2sf_tab[i] = 2<sup>i</sup>
			pow2_table[] is defined as:
			foreach i in 0..3
			pow2_table[i] = 2<sup>i/4</sup>

	== quant_to_spec(ic_stream ics, real spec_coeff[1024]) ==		== quant_to_spec(ic_stream ics, real spec_coeff[1024]) ==
Line 276:		Line 286:
	This function applies to the main profile.		This function applies to the main profile.

	== tns_decode_frame() ==		== tns_decode_frame(ic_stream ics, tns_info tns, int sample_rate_index, int object_type, real spec_coeff[1024]) ==
			tns = temporal noise shaping
			nshort = frame_length / 8 (frame_length is usually 1024)
			declare array of real called lpc[TNS_MAX_ORDER + 1] (TNS_MAX_ORDER = 20)
			if ics.tns_data_present == 0
			nothing to do in this phase
			'''(TODO)'''

	== drc_decode() ==		== drc_decode() ==

Multimedia Mike: /* apply_scalefactors(ic_string ics, real spec_coeff[1024]) */ simplify math expressions

2006-03-13T05:43:49Z

apply_scalefactors(ic_string ics, real spec_coeff[1024]): simplify math expressions

← Older revision		Revision as of 22:43, 12 March 2006
Line 72:		Line 72:
	top = ics.section_scalefactor_band_offset[g][scalefactor_band + 1]		top = ics.section_scalefactor_band_offset[g][scalefactor_band + 1]
	if (ics.scalefactors[g][scalefactor_band] < 0) OR (ics.scalefactors[g][scalefactor_band] > 255)		if (ics.scalefactors[g][scalefactor_band] < 0) OR (ics.scalefactors[g][scalefactor_band] > 255)
	~~exponent~~ = ~~fraction = 0~~		scale = 1
	else		else
	exponent = ics.scalefactors[g][scalefactor_band] ~~>> 2~~		exponent = (ics.scalefactors[g][scalefactor_band] - 100) / 4.0
	~~fraction~~ = ~~ics.scalefactors[g][scalefactor_band] & 3~~		scale = 2<sup>exponent</sup>
	while (k < top)		while (k < top)
	spec_coeff[k + (groups * nshort) + 0] *= ~~pow2sf_tab[exponent]~~		spec_coeff[k + (groups * nshort) + 0] *= scale
	~~spec_coeff[k + (groups * nshort) + 0] *= pow2_table[fraction]~~		spec_coeff[k + (groups * nshort) + 1] *= scale
	~~spec_coeff[k + (groups * nshort) + 1] *= pow2sf_tab[exponent]~~		spec_coeff[k + (groups * nshort) + 2] *= scale
	spec_coeff[k + (groups * nshort) + 1] *= ~~pow2_table[fraction]~~		spec_coeff[k + (groups * nshort) + 3] *= scale
	spec_coeff[k + (groups * nshort) + 2] *= ~~pow2sf_tab[exponent]~~
	~~spec_coeff[k + (groups * nshort) + 2] *= pow2_table[fraction]~~
	spec_coeff[k + (groups * nshort) + 3] *= ~~pow2sf_tab[exponent]~~
	~~spec_coeff[k + (groups * nshort) + 3] *= pow2_table[fraction]~~
	k += 4		k += 4
	groups += ics.window_group_length[g]		groups += ics.window_group_length[g]
	~~pow2sf_tab[] is defined as:~~
	~~foreach i in -25..38~~
	~~pow2sf_tab[i] = 2<sup>i</sup>~~
	~~pow2_table[] is defined as:~~
	~~foreach i in 0..3~~
	~~pow2_table[i] = 2<sup>i/4</sup>~~

	== quant_to_spec(ic_stream ics, real spec_coeff[1024]) ==		== quant_to_spec(ic_stream ics, real spec_coeff[1024]) ==