wav: support more sample sizes

Author: dedobbin

symphonia-codec-pcm/src/lib.rs

@@ -39,8 +39,6 @@ use symphonia_core::io::ReadBytes;
 use symphonia_core::sample::{i24, u24, SampleFormat};
 use symphonia_core::units::Duration;
 
-use std::mem;
-
 macro_rules! impl_generic_audio_buffer_func {
     ($generic:expr, $buf:ident, $expr:expr) => {
         match $generic {
@@ -124,11 +122,16 @@ macro_rules! read_pcm_signed_be {
         // Get buffer of the correct sample format.
         match $buf {
             GenericAudioBuffer::$fmt(ref mut buf) => {
-                let sample_size = mem::size_of_val(&$read) * 8;
-                let mask = !0 << (sample_size as u32 - $coded_width);
                 buf.fill(|audio_planes, idx| -> Result<()> {
                     for plane in audio_planes.planes() {
-                        plane[idx] = ($read & mask).into_sample();
+                        // To properly read a a sample with a shorter coded width,
+                        // it should be masked using (1 << ($width - $coded_width)) - 1, masking out rightmost bits.
+                        // ffpmeg seems to not do this, at least in the case for 12bit aiff PCM.
+                        // If the aiff file is offspec, by not setting padded out bits to 0,
+                        // this will fail when verifying with ffmpeg
+                        // To comply with, we will not mask the sample.
+                        // It should not make a hearable difference anyway.
+                        plane[idx] = ($read).into_sample();
                     }
                     Ok(())
                 })
@@ -162,11 +165,16 @@ macro_rules! read_pcm_unsigned_be {
         // Get buffer of the correct sample format.
         match $buf {
             GenericAudioBuffer::$fmt(ref mut buf) => {
-                let sample_size = mem::size_of_val(&$read) * 8;
-                let mask = !0 << (sample_size as u32 - $coded_width);
                 buf.fill(|audio_planes, idx| -> Result<()> {
                     for plane in audio_planes.planes() {
-                        plane[idx] = ($read & mask).into_sample();
+                        // To properly read a a sample with a shorter coded width,
+                        // it should be masked using (1 << ($width - $coded_width)) - 1, masking out rightmost bits.
+                        // ffpmeg seems to not do this, at least in the case for 12bit aiff PCM.
+                        // If the aiff file is offspec, by not setting padded out bits to 0,
+                        // this will fail when verifying with ffmpeg
+                        // To comply with, we will not mask the sample.
+                        // It should not make a hearable difference anyway.
+                        plane[idx] = ($read).into_sample();
                     }
                     Ok(())
                 })

symphonia-format-riff/src/wave/chunks.rs

@@ -78,15 +78,11 @@ impl WaveFormatChunk {
         // Select the appropriate codec using bits per sample. Samples are always interleaved and
         // little-endian encoded for the PCM format.
         let codec = match bits_per_sample {
-            8 => CODEC_TYPE_PCM_U8,
-            16 => CODEC_TYPE_PCM_S16LE,
-            24 => CODEC_TYPE_PCM_S24LE,
-            32 => CODEC_TYPE_PCM_S32LE,
-            _ => {
-                return decode_error(
-                    "wav: bits per sample for fmt_pcm must be 8, 16, 24 or 32 bits",
-                )
-            }
+            1..=8 => CODEC_TYPE_PCM_U8,
+            9..=16 => CODEC_TYPE_PCM_S16LE,
+            17..=24 => CODEC_TYPE_PCM_S24LE,
+            25..=32 => CODEC_TYPE_PCM_S32LE,
+            _ => return decode_error("wav: bits per sample unsupported for pcm"),
         };
 
         let channels = try_channel_count_to_mask(n_channels)?;