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refactor(processor): extract astats metadata into helper
- Add baseMetadataAccumulators.extractAstatsMetadata to centralise astats parsing - Move duplicated astats extraction and conversions into the new helper - convert CrestFactor from linear ratio to dB - convert MinLevel/MaxLevel from linear samples to dBFS - Replace inline extraction in extractFrameMetadata and extractOutputFrameMetadata - Reduce duplication and improve maintainability; no behavioural change Signed-off-by: Martin Wimpress <martin@wimpress.org>
1 parent 2354b64 commit ff6a045

1 file changed

Lines changed: 74 additions & 171 deletions

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‎internal/processor/analyzer.go‎

Lines changed: 74 additions & 171 deletions
Original file line numberDiff line numberDiff line change
@@ -1506,6 +1506,78 @@ func (b *baseMetadataAccumulators) accumulateSpectral(spectral spectralMetrics)
15061506
b.spectralFrameCount++
15071507
}
15081508

1509+
// extractAstatsMetadata extracts all astats measurements from FFmpeg metadata.
1510+
// These are cumulative values, so we keep the latest from each frame.
1511+
// Includes conversions: linearRatioToDB for CrestFactor, linearSampleToDBFS for MinLevel/MaxLevel.
1512+
func (b *baseMetadataAccumulators) extractAstatsMetadata(metadata *ffmpeg.AVDictionary) {
1513+
if value, ok := getFloatMetadata(metadata, metaKeyDynamicRange); ok {
1514+
b.astatsDynamicRange = value
1515+
b.astatsFound = true
1516+
}
1517+
if value, ok := getFloatMetadata(metadata, metaKeyRMSLevel); ok {
1518+
b.astatsRMSLevel = value
1519+
}
1520+
if value, ok := getFloatMetadata(metadata, metaKeyPeakLevel); ok {
1521+
b.astatsPeakLevel = value
1522+
}
1523+
if value, ok := getFloatMetadata(metadata, metaKeyRMSTrough); ok {
1524+
b.astatsRMSTrough = value
1525+
}
1526+
if value, ok := getFloatMetadata(metadata, metaKeyRMSPeak); ok {
1527+
b.astatsRMSPeak = value
1528+
}
1529+
if value, ok := getFloatMetadata(metadata, metaKeyDCOffset); ok {
1530+
b.astatsDCOffset = value
1531+
}
1532+
if value, ok := getFloatMetadata(metadata, metaKeyFlatFactor); ok {
1533+
b.astatsFlatFactor = value
1534+
}
1535+
// CrestFactor: FFmpeg reports as linear ratio (peak/RMS), convert to dB
1536+
if value, ok := getFloatMetadata(metadata, metaKeyCrestFactor); ok {
1537+
b.astatsCrestFactor = linearRatioToDB(value)
1538+
}
1539+
if value, ok := getFloatMetadata(metadata, metaKeyZeroCrossingsRate); ok {
1540+
b.astatsZeroCrossingsRate = value
1541+
}
1542+
if value, ok := getFloatMetadata(metadata, metaKeyZeroCrossings); ok {
1543+
b.astatsZeroCrossings = value
1544+
}
1545+
if value, ok := getFloatMetadata(metadata, metaKeyMaxDifference); ok {
1546+
b.astatsMaxDifference = value
1547+
}
1548+
if value, ok := getFloatMetadata(metadata, metaKeyMinDifference); ok {
1549+
b.astatsMinDifference = value
1550+
}
1551+
if value, ok := getFloatMetadata(metadata, metaKeyMeanDifference); ok {
1552+
b.astatsMeanDifference = value
1553+
}
1554+
if value, ok := getFloatMetadata(metadata, metaKeyRMSDifference); ok {
1555+
b.astatsRMSDifference = value
1556+
}
1557+
if value, ok := getFloatMetadata(metadata, metaKeyEntropy); ok {
1558+
b.astatsEntropy = value
1559+
}
1560+
// MinLevel/MaxLevel: FFmpeg reports as linear sample values, convert to dBFS
1561+
if value, ok := getFloatMetadata(metadata, metaKeyMinLevel); ok {
1562+
b.astatsMinLevel = linearSampleToDBFS(value)
1563+
}
1564+
if value, ok := getFloatMetadata(metadata, metaKeyMaxLevel); ok {
1565+
b.astatsMaxLevel = linearSampleToDBFS(value)
1566+
}
1567+
if value, ok := getFloatMetadata(metadata, metaKeyNoiseFloor); ok {
1568+
b.astatsNoiseFloor = value
1569+
}
1570+
if value, ok := getFloatMetadata(metadata, metaKeyNoiseFloorCount); ok {
1571+
b.astatsNoiseFloorCount = value
1572+
}
1573+
if value, ok := getFloatMetadata(metadata, metaKeyBitDepth); ok {
1574+
b.astatsBitDepth = value
1575+
}
1576+
if value, ok := getFloatMetadata(metadata, metaKeyNumberOfSamples); ok {
1577+
b.astatsNumberOfSamples = value
1578+
}
1579+
}
1580+
15091581
// metadataAccumulators holds accumulator variables for Pass 1 frame metadata extraction.
15101582
// Uses baseMetadataAccumulators for spectral and astats fields shared with output analysis.
15111583
type metadataAccumulators struct {
@@ -1704,111 +1776,7 @@ func extractFrameMetadata(metadata *ffmpeg.AVDictionary, acc *metadataAccumulato
17041776

17051777
// Extract astats measurements (cumulative, so we keep the latest)
17061778
// For mono audio, stats are under channel .1
1707-
if value, ok := getFloatMetadata(metadata, metaKeyDynamicRange); ok {
1708-
acc.astatsDynamicRange = value
1709-
acc.astatsFound = true
1710-
}
1711-
1712-
if value, ok := getFloatMetadata(metadata, metaKeyRMSLevel); ok {
1713-
acc.astatsRMSLevel = value
1714-
}
1715-
1716-
if value, ok := getFloatMetadata(metadata, metaKeyPeakLevel); ok {
1717-
acc.astatsPeakLevel = value
1718-
}
1719-
1720-
// Extract RMS_trough - RMS level of quietest segments (best noise floor indicator for speech)
1721-
// In speech audio, quiet inter-word periods contain primarily ambient/electronic noise
1722-
if value, ok := getFloatMetadata(metadata, metaKeyRMSTrough); ok {
1723-
acc.astatsRMSTrough = value
1724-
}
1725-
1726-
// Extract RMS_peak - RMS level of loudest segments
1727-
if value, ok := getFloatMetadata(metadata, metaKeyRMSPeak); ok {
1728-
acc.astatsRMSPeak = value
1729-
}
1730-
1731-
// Extract DC_offset - mean amplitude displacement from zero
1732-
// High values indicate DC bias that should be removed before processing
1733-
if value, ok := getFloatMetadata(metadata, metaKeyDCOffset); ok {
1734-
acc.astatsDCOffset = value
1735-
}
1736-
1737-
// Extract Flat_factor - consecutive samples at peak levels (indicates clipping)
1738-
// High values suggest pre-existing limiting or clipping damage
1739-
if value, ok := getFloatMetadata(metadata, metaKeyFlatFactor); ok {
1740-
acc.astatsFlatFactor = value
1741-
}
1742-
1743-
// Extract Crest_factor - FFmpeg reports as linear ratio (peak/RMS), convert to dB
1744-
// High values indicate impulsive/dynamic content, low values indicate compressed/limited audio
1745-
if value, ok := getFloatMetadata(metadata, metaKeyCrestFactor); ok {
1746-
acc.astatsCrestFactor = linearRatioToDB(value)
1747-
}
1748-
1749-
// Extract Zero_crossings_rate - rate of zero crossings per sample
1750-
// Low ZCR = bass-heavy/sustained tones, High ZCR = noise/sibilance
1751-
if value, ok := getFloatMetadata(metadata, metaKeyZeroCrossingsRate); ok {
1752-
acc.astatsZeroCrossingsRate = value
1753-
}
1754-
1755-
// Extract Zero_crossings - total number of zero crossings
1756-
if value, ok := getFloatMetadata(metadata, metaKeyZeroCrossings); ok {
1757-
acc.astatsZeroCrossings = value
1758-
}
1759-
1760-
// Extract Max_difference - largest sample-to-sample change
1761-
// High values indicate impulsive sounds (clicks, pops)
1762-
if value, ok := getFloatMetadata(metadata, metaKeyMaxDifference); ok {
1763-
acc.astatsMaxDifference = value
1764-
}
1765-
1766-
// Extract Min_difference - smallest sample-to-sample change
1767-
if value, ok := getFloatMetadata(metadata, metaKeyMinDifference); ok {
1768-
acc.astatsMinDifference = value
1769-
}
1770-
1771-
// Extract Mean_difference - average sample-to-sample change
1772-
if value, ok := getFloatMetadata(metadata, metaKeyMeanDifference); ok {
1773-
acc.astatsMeanDifference = value
1774-
}
1775-
1776-
// Extract RMS_difference - RMS of sample-to-sample changes
1777-
if value, ok := getFloatMetadata(metadata, metaKeyRMSDifference); ok {
1778-
acc.astatsRMSDifference = value
1779-
}
1780-
1781-
// Extract Entropy - signal randomness (1.0 = white noise, lower = more structured)
1782-
if value, ok := getFloatMetadata(metadata, metaKeyEntropy); ok {
1783-
acc.astatsEntropy = value
1784-
}
1785-
1786-
// Extract Min_level and Max_level - FFmpeg reports as linear sample values, convert to dBFS
1787-
if value, ok := getFloatMetadata(metadata, metaKeyMinLevel); ok {
1788-
acc.astatsMinLevel = linearSampleToDBFS(value)
1789-
}
1790-
if value, ok := getFloatMetadata(metadata, metaKeyMaxLevel); ok {
1791-
acc.astatsMaxLevel = linearSampleToDBFS(value)
1792-
}
1793-
1794-
// Extract Noise_floor - FFmpeg's own noise floor estimate (dBFS)
1795-
// Very useful for adaptive gate/noise reduction thresholds
1796-
if value, ok := getFloatMetadata(metadata, metaKeyNoiseFloor); ok {
1797-
acc.astatsNoiseFloor = value
1798-
}
1799-
if value, ok := getFloatMetadata(metadata, metaKeyNoiseFloorCount); ok {
1800-
acc.astatsNoiseFloorCount = value
1801-
}
1802-
1803-
// Extract Bit_depth - effective bit depth of audio
1804-
if value, ok := getFloatMetadata(metadata, metaKeyBitDepth); ok {
1805-
acc.astatsBitDepth = value
1806-
}
1807-
1808-
// Extract Number_of_samples - total samples processed
1809-
if value, ok := getFloatMetadata(metadata, metaKeyNumberOfSamples); ok {
1810-
acc.astatsNumberOfSamples = value
1811-
}
1779+
acc.extractAstatsMetadata(metadata)
18121780

18131781
// Extract ebur128 measurements (cumulative loudness analysis)
18141782
// ebur128 provides: M (momentary 400ms), S (short-term 3s), I (integrated), LRA, sample_peak, true_peak
@@ -2048,72 +2016,7 @@ func extractOutputFrameMetadata(metadata *ffmpeg.AVDictionary, acc *outputMetada
20482016
acc.accumulateSpectral(extractSpectralMetrics(metadata))
20492017

20502018
// Extract astats measurements (cumulative, so we keep the latest)
2051-
if value, ok := getFloatMetadata(metadata, metaKeyDynamicRange); ok {
2052-
acc.astatsDynamicRange = value
2053-
acc.astatsFound = true
2054-
}
2055-
if value, ok := getFloatMetadata(metadata, metaKeyRMSLevel); ok {
2056-
acc.astatsRMSLevel = value
2057-
}
2058-
if value, ok := getFloatMetadata(metadata, metaKeyPeakLevel); ok {
2059-
acc.astatsPeakLevel = value
2060-
}
2061-
if value, ok := getFloatMetadata(metadata, metaKeyRMSTrough); ok {
2062-
acc.astatsRMSTrough = value
2063-
}
2064-
if value, ok := getFloatMetadata(metadata, metaKeyRMSPeak); ok {
2065-
acc.astatsRMSPeak = value
2066-
}
2067-
if value, ok := getFloatMetadata(metadata, metaKeyDCOffset); ok {
2068-
acc.astatsDCOffset = value
2069-
}
2070-
if value, ok := getFloatMetadata(metadata, metaKeyFlatFactor); ok {
2071-
acc.astatsFlatFactor = value
2072-
}
2073-
// CrestFactor: FFmpeg reports as linear ratio (peak/RMS), convert to dB
2074-
if value, ok := getFloatMetadata(metadata, metaKeyCrestFactor); ok {
2075-
acc.astatsCrestFactor = linearRatioToDB(value)
2076-
}
2077-
if value, ok := getFloatMetadata(metadata, metaKeyZeroCrossingsRate); ok {
2078-
acc.astatsZeroCrossingsRate = value
2079-
}
2080-
if value, ok := getFloatMetadata(metadata, metaKeyZeroCrossings); ok {
2081-
acc.astatsZeroCrossings = value
2082-
}
2083-
if value, ok := getFloatMetadata(metadata, metaKeyMaxDifference); ok {
2084-
acc.astatsMaxDifference = value
2085-
}
2086-
if value, ok := getFloatMetadata(metadata, metaKeyMinDifference); ok {
2087-
acc.astatsMinDifference = value
2088-
}
2089-
if value, ok := getFloatMetadata(metadata, metaKeyMeanDifference); ok {
2090-
acc.astatsMeanDifference = value
2091-
}
2092-
if value, ok := getFloatMetadata(metadata, metaKeyRMSDifference); ok {
2093-
acc.astatsRMSDifference = value
2094-
}
2095-
if value, ok := getFloatMetadata(metadata, metaKeyEntropy); ok {
2096-
acc.astatsEntropy = value
2097-
}
2098-
// MinLevel/MaxLevel: FFmpeg reports as linear sample values, convert to dBFS
2099-
if value, ok := getFloatMetadata(metadata, metaKeyMinLevel); ok {
2100-
acc.astatsMinLevel = linearSampleToDBFS(value)
2101-
}
2102-
if value, ok := getFloatMetadata(metadata, metaKeyMaxLevel); ok {
2103-
acc.astatsMaxLevel = linearSampleToDBFS(value)
2104-
}
2105-
if value, ok := getFloatMetadata(metadata, metaKeyNoiseFloor); ok {
2106-
acc.astatsNoiseFloor = value
2107-
}
2108-
if value, ok := getFloatMetadata(metadata, metaKeyNoiseFloorCount); ok {
2109-
acc.astatsNoiseFloorCount = value
2110-
}
2111-
if value, ok := getFloatMetadata(metadata, metaKeyBitDepth); ok {
2112-
acc.astatsBitDepth = value
2113-
}
2114-
if value, ok := getFloatMetadata(metadata, metaKeyNumberOfSamples); ok {
2115-
acc.astatsNumberOfSamples = value
2116-
}
2019+
acc.extractAstatsMetadata(metadata)
21172020

21182021
// Extract ebur128 measurements
21192022
if value, ok := getFloatMetadata(metadata, metaKeyEbur128I); ok {

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