lib/util/flac.cpp: Add support for flac data where bits_per_sample != 16. #11848

wilbertpol · 2023-12-17T17:58:43Z

No description provided.

… 16.

ICEknigh7 · 2023-12-17T23:03:53Z

Seems to work fine with the 24 bit FLACs I've been trying on the Spectrum core (even better than WAV support, actually).

The only "problem" I've found is that it's only possible to play the Left channel (akin to loading from a Stereo source, rather than the recommended Monaural which would do the audio sum of both channels), but I suppose that's likely caused by something in the drivers themselves and not because of the FLAC decoding.

wilbertpol · 2023-12-17T23:42:21Z

The only "problem" I've found is that it's only possible to play the Left channel (akin to loading from a Stereo source, rather than the recommended Monaural which would do the audio sum of both channels), but I suppose that's likely caused by something in the drivers themselves and not because of the FLAC decoding.

Partially; the driver needs to do a set_stereo() on the cassette device (currently there seem to be no drivers using this). And it also needs this small change:

--- a/src/devices/imagedev/cassette.cpp
+++ b/src/devices/imagedev/cassette.cpp
@@ -452,7 +452,7 @@ void cassette_image_device::sound_stream_update(sound_stream &stream, std::vecto
 
                for (int ch = 0; ch < outputs.size(); ch++)
                {
-                       cassette->get_samples(0, time_index, duration, outputs[0].samples(), 2, &m_samples[0], cassette_image::WAVEFORM_16BIT);
+                       cassette->get_samples(ch, time_index, duration, outputs[0].samples(), 2, &m_samples[0], cassette_image::WAVEFORM_16BIT);
                        for (int sampindex = 0; sampindex < outputs[ch].samples(); sampindex++)
                                outputs[ch].put_int(sampindex, m_samples[sampindex], 32768);
                }

That fixed channels for flacs but gave me some weird echoing results on wavs before; it could be that I tested it wrongly though.

wilbertpol · 2023-12-18T09:09:12Z

It also works with 8 bit flacs. For example, abcstack from the abc80_cass software list converted to flac. This never worked for me before.

cuavas · 2023-12-19T01:47:44Z

src/lib/util/flac.cpp

+	if (m_uncompressed_swap)
+	{
+		sample = FLAC__int32(((uint32_t(sample) >> 24) & 0x000000ff) | ((uint32_t(sample) >> 16) & 0x0000ff00) | ((uint32_t(sample) >> 8) & 0x00ff0000) | (uint32_t(sample) & 0xff000000));
+	}


You could use swapendian_int32 from osdcomn.h

cuavas · 2023-12-19T01:48:44Z

src/lib/util/flac.cpp

+int16_t flac_decoder::convert_to_int16(const ::FLAC__Frame *frame, FLAC__int32 sample)
+{


Is there a reason this isn’t const qualified? It shouldn’t change decoder state.

No, made it const.

cuavas · 2023-12-19T01:51:07Z

src/lib/util/flac.cpp

+	if (frame->header.bits_per_sample >= 16)
+		return int16_t(uint32_t(sample >> (frame->header.bits_per_sample - 16)));
+	else
+		return int16_t(uint32_t(sample << (16 - frame->header.bits_per_sample)));


You should round towards even when reducing resolution, and you should splat right when increasing resolution.

cuavas · 2023-12-19T01:53:20Z

src/lib/util/flac.cpp

+	if (m_uncompressed_swap)
+	{
+		sample = FLAC__int32(((uint32_t(sample) >> 24) & 0x000000ff) | ((uint32_t(sample) >> 16) & 0x0000ff00) | ((uint32_t(sample) >> 8) & 0x00ff0000) | (uint32_t(sample) & 0xff000000));
+	}
+	if (frame->header.bits_per_sample >= 16)
+		return int16_t(uint32_t(sample >> (frame->header.bits_per_sample - 16)));
+	else
+		return int16_t(uint32_t(sample << (16 - frame->header.bits_per_sample)));


This won’t work if the output format isn’t native Endianness. You’re converting to output format before trying to adjust resolution. Do this on paper and see what happens.

Yes, I had the operations swapped.

…dian change operations.

… does.

cuavas

The trouble with this is it’s a massive pessimisation. Remember this is going to be run for tens of thousands of samples at the very least. The current code is written with pipeline performance in mind – shifts are pre-calculated before the loop so the actual format conversion in the loop doesn’t require any conditional code.

With this change, tests based on input and output formats are being done for every sample.

Please think about how you can restructure the code to lift as much conditional code out of the loop as possible, and to make the code in the loop work with conditional moves rather than requiring more expensive branches.

Also, that doesn’t round towards even – it rounds towards positive infinity.

wilbertpol · 2023-12-22T23:27:12Z

I have moved most of the old conditional code outside the loop by using templating.

… 16. (mamedev#11848)

lib/util/flac.cpp: Add support for flac data where bits_per_sample !=…

29b97fa

… 16.

wilbertpol mentioned this pull request Dec 17, 2023

New not working system & software list: Sega AI #11747

Merged

cuavas reviewed Dec 19, 2023

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wilbertpol added 2 commits December 19, 2023 10:01

lib/util/flac.cpp: Mark convert_to_int16 const. Swap the shift and en…

ac67f0d

…dian change operations.

lib/util/flac.cpp: Set m_bits_per_sample to match what write_callback…

87d7dbd

… does.

cuavas requested changes Dec 22, 2023

View reviewed changes

wilbertpol added 2 commits December 22, 2023 23:06

Replace convert_to_int16 by templating write_callback.

f950d68

Unroll first iteration of the scale up loops.

9faf085

Simplify by taking a repeated calculation out of the main loop.

7bd2eb8

rb6502 merged commit 9c95144 into mamedev:master Dec 31, 2023
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wilbertpol deleted the flac_bps branch February 13, 2024 20:58

einstein95 pushed a commit to einstein95/mame that referenced this pull request Mar 2, 2024

lib/util/flac.cpp: Add support for flac data where bits_per_sample !=…

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… 16. (mamedev#11848)

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lib/util/flac.cpp: Add support for flac data where bits_per_sample != 16. #11848

lib/util/flac.cpp: Add support for flac data where bits_per_sample != 16. #11848

wilbertpol commented Dec 17, 2023

ICEknigh7 commented Dec 17, 2023 •

edited by wilbertpol

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		int16_t flac_decoder::convert_to_int16(const ::FLAC__Frame *frame, FLAC__int32 sample)
		{

lib/util/flac.cpp: Add support for flac data where bits_per_sample != 16. #11848

lib/util/flac.cpp: Add support for flac data where bits_per_sample != 16. #11848

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