From e55f9b42e9f1f51f1d4af4537d10dbf63c55d4e5 Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Sun, 27 Jan 2019 14:53:46 -0800
Subject: Partially handle ambisonics in alffplay
This is currently really only applicable to Opus-encoded files. It assumes
AmbiX (SN3D normalization, ACN ordering) and only comes into play when the
channel layout is blank. FFmpeg/libavcodec doesn't have a way to detect
B-Format input or what normalization and ordering it uses. Note in particular
.amb files do not play correctly (libavcodec seems to apply a default channel
layout for 4-channel wav-type files, regardless of its channel mask value).
---
examples/alffplay.cpp | 126 +++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 98 insertions(+), 28 deletions(-)
(limited to 'examples')
diff --git a/examples/alffplay.cpp b/examples/alffplay.cpp
index 0375aecc..28b968e2 100644
--- a/examples/alffplay.cpp
+++ b/examples/alffplay.cpp
@@ -85,6 +85,8 @@ typedef void (AL_APIENTRY*LPALGETPOINTERVSOFT)(ALenum pname, void **values);
namespace {
+inline constexpr int64_t operator "" _i64(unsigned long long int n) noexcept { return static_cast<int64_t>(n); }
+
#ifndef M_PI
#define M_PI (3.14159265358979323846)
#endif
@@ -146,7 +148,7 @@ enum class SyncMaster {
inline microseconds get_avtime()
-{ return microseconds(av_gettime()); }
+{ return microseconds{av_gettime()}; }
/* Define unique_ptrs to auto-cleanup associated ffmpeg objects. */
struct AVIOContextDeleter {
@@ -286,7 +288,7 @@ struct AudioState {
nanoseconds getClockNoLock();
nanoseconds getClock()
{
- std::lock_guard<std::mutex> lock(mSrcMutex);
+ std::lock_guard<std::mutex> lock{mSrcMutex};
return getClockNoLock();
}
@@ -771,13 +773,15 @@ int AudioState::handler()
/* Find a suitable format for OpenAL. */
mDstChanLayout = 0;
- if(mCodecCtx->sample_fmt == AV_SAMPLE_FMT_U8 || mCodecCtx->sample_fmt == AV_SAMPLE_FMT_U8P)
+ mFormat = AL_NONE;
+ if((mCodecCtx->sample_fmt == AV_SAMPLE_FMT_FLT || mCodecCtx->sample_fmt == AV_SAMPLE_FMT_FLTP) &&
+ alIsExtensionPresent("AL_EXT_FLOAT32"))
{
- mDstSampleFmt = AV_SAMPLE_FMT_U8;
- mFrameSize = 1;
+ mDstSampleFmt = AV_SAMPLE_FMT_FLT;
+ mFrameSize = 4;
if(mCodecCtx->channel_layout == AV_CH_LAYOUT_7POINT1 &&
alIsExtensionPresent("AL_EXT_MCFORMATS") &&
- (fmt=alGetEnumValue("AL_FORMAT_71CHN8")) != AL_NONE && fmt != -1)
+ (fmt=alGetEnumValue("AL_FORMAT_71CHN32")) != AL_NONE && fmt != -1)
{
mDstChanLayout = mCodecCtx->channel_layout;
mFrameSize *= 8;
@@ -786,7 +790,7 @@ int AudioState::handler()
if((mCodecCtx->channel_layout == AV_CH_LAYOUT_5POINT1 ||
mCodecCtx->channel_layout == AV_CH_LAYOUT_5POINT1_BACK) &&
alIsExtensionPresent("AL_EXT_MCFORMATS") &&
- (fmt=alGetEnumValue("AL_FORMAT_51CHN8")) != AL_NONE && fmt != -1)
+ (fmt=alGetEnumValue("AL_FORMAT_51CHN32")) != AL_NONE && fmt != -1)
{
mDstChanLayout = mCodecCtx->channel_layout;
mFrameSize *= 6;
@@ -796,23 +800,42 @@ int AudioState::handler()
{
mDstChanLayout = mCodecCtx->channel_layout;
mFrameSize *= 1;
- mFormat = AL_FORMAT_MONO8;
+ mFormat = AL_FORMAT_MONO_FLOAT32;
+ }
+ /* Assume 3D B-Format (ambisonics) if the channel layout is blank and
+ * there's 4 or more channels. FFmpeg/libavcodec otherwise seems to
+ * have no way to specify if the source is actually B-Format (let alone
+ * if it's 2D or 3D).
+ */
+ if(mCodecCtx->channel_layout == 0 && mCodecCtx->channels >= 4 &&
+ alIsExtensionPresent("AL_EXT_BFORMAT") &&
+ (fmt=alGetEnumValue("AL_FORMAT_BFORMAT3D_FLOAT32")) != AL_NONE && fmt != -1)
+ {
+ int order{static_cast<int>(std::sqrt(mCodecCtx->channels)) - 1};
+ if((order+1)*(order+1) == mCodecCtx->channels ||
+ (order+1)*(order+1) + 2 == mCodecCtx->channels)
+ {
+ /* OpenAL only supports first-order with AL_EXT_BFORMAT, which
+ * is 4 channels for 3D buffers.
+ */
+ mFrameSize *= 4;
+ mFormat = fmt;
+ }
}
- if(!mDstChanLayout)
+ if(!mFormat)
{
mDstChanLayout = AV_CH_LAYOUT_STEREO;
mFrameSize *= 2;
- mFormat = AL_FORMAT_STEREO8;
+ mFormat = AL_FORMAT_STEREO_FLOAT32;
}
}
- if((mCodecCtx->sample_fmt == AV_SAMPLE_FMT_FLT || mCodecCtx->sample_fmt == AV_SAMPLE_FMT_FLTP) &&
- alIsExtensionPresent("AL_EXT_FLOAT32"))
+ if(mCodecCtx->sample_fmt == AV_SAMPLE_FMT_U8 || mCodecCtx->sample_fmt == AV_SAMPLE_FMT_U8P)
{
- mDstSampleFmt = AV_SAMPLE_FMT_FLT;
- mFrameSize = 4;
+ mDstSampleFmt = AV_SAMPLE_FMT_U8;
+ mFrameSize = 1;
if(mCodecCtx->channel_layout == AV_CH_LAYOUT_7POINT1 &&
alIsExtensionPresent("AL_EXT_MCFORMATS") &&
- (fmt=alGetEnumValue("AL_FORMAT_71CHN32")) != AL_NONE && fmt != -1)
+ (fmt=alGetEnumValue("AL_FORMAT_71CHN8")) != AL_NONE && fmt != -1)
{
mDstChanLayout = mCodecCtx->channel_layout;
mFrameSize *= 8;
@@ -821,7 +844,7 @@ int AudioState::handler()
if((mCodecCtx->channel_layout == AV_CH_LAYOUT_5POINT1 ||
mCodecCtx->channel_layout == AV_CH_LAYOUT_5POINT1_BACK) &&
alIsExtensionPresent("AL_EXT_MCFORMATS") &&
- (fmt=alGetEnumValue("AL_FORMAT_51CHN32")) != AL_NONE && fmt != -1)
+ (fmt=alGetEnumValue("AL_FORMAT_51CHN8")) != AL_NONE && fmt != -1)
{
mDstChanLayout = mCodecCtx->channel_layout;
mFrameSize *= 6;
@@ -831,16 +854,28 @@ int AudioState::handler()
{
mDstChanLayout = mCodecCtx->channel_layout;
mFrameSize *= 1;
- mFormat = AL_FORMAT_MONO_FLOAT32;
+ mFormat = AL_FORMAT_MONO8;
+ }
+ if(mCodecCtx->channel_layout == 0 && mCodecCtx->channels >= 4 &&
+ alIsExtensionPresent("AL_EXT_BFORMAT") &&
+ (fmt=alGetEnumValue("AL_FORMAT_BFORMAT3D8")) != AL_NONE && fmt != -1)
+ {
+ int order{static_cast<int>(std::sqrt(mCodecCtx->channels)) - 1};
+ if((order+1)*(order+1) == mCodecCtx->channels ||
+ (order+1)*(order+1) + 2 == mCodecCtx->channels)
+ {
+ mFrameSize *= 4;
+ mFormat = fmt;
+ }
}
- if(!mDstChanLayout)
+ if(!mFormat)
{
mDstChanLayout = AV_CH_LAYOUT_STEREO;
mFrameSize *= 2;
- mFormat = AL_FORMAT_STEREO_FLOAT32;
+ mFormat = AL_FORMAT_STEREO8;
}
}
- if(!mDstChanLayout)
+ if(!mFormat)
{
mDstSampleFmt = AV_SAMPLE_FMT_S16;
mFrameSize = 2;
@@ -867,7 +902,19 @@ int AudioState::handler()
mFrameSize *= 1;
mFormat = AL_FORMAT_MONO16;
}
- if(!mDstChanLayout)
+ if(mCodecCtx->channel_layout == 0 && mCodecCtx->channels >= 4 &&
+ alIsExtensionPresent("AL_EXT_BFORMAT") &&
+ (fmt=alGetEnumValue("AL_FORMAT_BFORMAT3D16")) != AL_NONE && fmt != -1)
+ {
+ int order{static_cast<int>(std::sqrt(mCodecCtx->channels)) - 1};
+ if((order+1)*(order+1) == mCodecCtx->channels ||
+ (order+1)*(order+1) + 2 == mCodecCtx->channels)
+ {
+ mFrameSize *= 4;
+ mFormat = fmt;
+ }
+ }
+ if(!mFormat)
{
mDstChanLayout = AV_CH_LAYOUT_STEREO;
mFrameSize *= 2;
@@ -890,13 +937,36 @@ int AudioState::handler()
goto finish;
}
- mSwresCtx.reset(swr_alloc_set_opts(nullptr,
- mDstChanLayout, mDstSampleFmt, mCodecCtx->sample_rate,
- mCodecCtx->channel_layout ? mCodecCtx->channel_layout :
- static_cast<uint64_t>(av_get_default_channel_layout(mCodecCtx->channels)),
- mCodecCtx->sample_fmt, mCodecCtx->sample_rate,
- 0, nullptr
- ));
+ if(!mDstChanLayout)
+ {
+ /* OpenAL only supports first-order ambisonics with AL_EXT_BFORMAT, so
+ * we have to drop any extra channels. It also only supports FuMa
+ * channel ordering and normalization, so a custom matrix is needed to
+ * scale and reorder the source from AmbiX.
+ */
+ mSwresCtx.reset(swr_alloc_set_opts(nullptr,
+ (1_i64<<4)-1, mDstSampleFmt, mCodecCtx->sample_rate,
+ (1_i64<<mCodecCtx->channels)-1, mCodecCtx->sample_fmt, mCodecCtx->sample_rate,
+ 0, nullptr));
+
+ /* Note that ffmpeg/libavcodec has no method to check the ambisonic
+ * channel order and normalization, so we can only assume AmbiX as the
+ * defacto-standard. This is not true for .amb files, which use FuMa.
+ */
+ std::vector<double> mtx(64*64, 0.0);
+ mtx[0 + 0*64] = std::sqrt(0.5);
+ mtx[3 + 1*64] = 1.0;
+ mtx[1 + 2*64] = 1.0;
+ mtx[2 + 3*64] = 1.0;
+ swr_set_matrix(mSwresCtx.get(), mtx.data(), 64);
+ }
+ else
+ mSwresCtx.reset(swr_alloc_set_opts(nullptr,
+ mDstChanLayout, mDstSampleFmt, mCodecCtx->sample_rate,
+ mCodecCtx->channel_layout ? mCodecCtx->channel_layout :
+ static_cast<uint64_t>(av_get_default_channel_layout(mCodecCtx->channels)),
+ mCodecCtx->sample_fmt, mCodecCtx->sample_rate,
+ 0, nullptr));
if(!mSwresCtx || swr_init(mSwresCtx.get()) != 0)
{
std::cerr<< "Failed to initialize audio converter" <<std::endl;
--
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