Lightningbeam/daw-backend/src/audio/export.rs

1054 lines
38 KiB
Rust

use super::buffer_pool::BufferPool;
use super::pool::AudioPool;
use super::project::Project;
use crate::command::AudioEvent;
use crate::tempo_map::TempoMap;
use crate::time::Seconds;
use std::path::Path;
/// Render chunk size for offline export. Matches the real-time playback buffer size
/// so that MIDI events are processed at the same granularity, avoiding timing jitter.
const EXPORT_CHUNK_FRAMES: usize = 256;
/// Supported export formats
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ExportFormat {
Wav,
Flac,
Mp3,
Aac,
}
impl ExportFormat {
/// Get the file extension for this format
pub fn extension(&self) -> &'static str {
match self {
ExportFormat::Wav => "wav",
ExportFormat::Flac => "flac",
ExportFormat::Mp3 => "mp3",
ExportFormat::Aac => "m4a",
}
}
}
/// Export settings for rendering audio
#[derive(Debug, Clone)]
pub struct ExportSettings {
/// Output format
pub format: ExportFormat,
/// Sample rate for export
pub sample_rate: u32,
/// Number of channels (1 = mono, 2 = stereo)
pub channels: u32,
/// Bit depth (16 or 24) - only for WAV/FLAC
pub bit_depth: u16,
/// MP3 bitrate in kbps (128, 192, 256, 320)
pub mp3_bitrate: u32,
/// Start time
pub start_time: Seconds,
/// End time
pub end_time: Seconds,
/// Tempo map for beat-position scheduling
pub tempo_map: TempoMap,
/// Tag metadata as (ffmpeg-key, value) pairs (e.g. ("title", "…"), ("artist", "…")). Written to
/// the container's native tags: ID3v2 (MP3), MP4 atoms (M4A), Vorbis comments (FLAC), RIFF INFO
/// (WAV). Empty = no tags.
pub metadata: Vec<(String, String)>,
}
impl Default for ExportSettings {
fn default() -> Self {
Self {
format: ExportFormat::Wav,
sample_rate: 44100,
channels: 2,
bit_depth: 16,
mp3_bitrate: 320,
start_time: Seconds::ZERO,
end_time: Seconds(60.0),
tempo_map: TempoMap::constant(120.0),
metadata: Vec::new(),
}
}
}
/// Set tag metadata on an ffmpeg output context (before `write_header`). FFmpeg maps the standard
/// keys to each container's native tags.
fn apply_metadata(output: &mut ffmpeg_next::format::context::Output, metadata: &[(String, String)]) {
if metadata.is_empty() {
return;
}
let mut dict = ffmpeg_next::Dictionary::new();
for (k, v) in metadata {
if !v.is_empty() {
dict.set(k, v);
}
}
output.set_metadata(dict);
}
/// Export the project to an audio file
///
/// This performs offline rendering, processing the entire timeline
/// in chunks to generate the final audio file.
///
/// If an event producer is provided, progress events will be sent
/// after each chunk with (frames_rendered, total_frames).
pub fn export_audio<P: AsRef<Path>>(
project: &mut Project,
pool: &AudioPool,
settings: &ExportSettings,
output_path: P,
mut event_tx: Option<&mut rtrb::Producer<AudioEvent>>,
) -> Result<(), String>
{
// Validate duration
let duration = settings.end_time - settings.start_time;
if duration <= Seconds::ZERO {
return Err(format!(
"Export duration is zero or negative (start={:.3}s, end={:.3}s). \
Check that the timeline has content.",
settings.start_time.seconds_to_f64(), settings.end_time.seconds_to_f64()
));
}
let total_frames = (duration.seconds_to_f64() * settings.sample_rate as f64).round() as usize;
if total_frames == 0 {
return Err("Export would produce zero audio frames".to_string());
}
// Reset all node graphs to clear stale effect buffers (echo, reverb, etc.)
project.reset_all_graphs();
// Enable blocking mode on all read-ahead buffers so compressed audio
// streams block until decoded frames are available (instead of returning
// silence when the disk reader hasn't caught up with offline rendering).
project.set_export_mode(true);
// Route to appropriate export implementation based on format.
// Ensure export mode is disabled even if an error occurs.
let result = match settings.format {
ExportFormat::Wav => {
let samples = render_to_memory(project, pool, settings, event_tx.as_mut().map(|tx| &mut **tx))?;
if let Some(ref mut tx) = event_tx {
let _ = tx.push(AudioEvent::ExportFinalizing);
}
write_wav(&samples, settings, &output_path)
// hound writes no metadata; append a RIFF INFO chunk for tags.
.and_then(|_| append_wav_info_chunk(output_path.as_ref(), &settings.metadata))
}
ExportFormat::Flac => {
let samples = render_to_memory(project, pool, settings, event_tx.as_mut().map(|tx| &mut **tx))?;
if let Some(ref mut tx) = event_tx {
let _ = tx.push(AudioEvent::ExportFinalizing);
}
export_flac(&samples, settings, &output_path)
}
ExportFormat::Mp3 => {
export_mp3(project, pool, settings, output_path, event_tx)
}
ExportFormat::Aac => {
export_aac(project, pool, settings, output_path, event_tx)
}
};
// Always disable export mode, even on error
project.set_export_mode(false);
result
}
/// Render the project to memory
///
/// This function renders the project's audio to an in-memory buffer
/// of interleaved f32 samples. This is useful for custom export formats
/// or for passing audio to external encoders (e.g., FFmpeg for MP3/AAC).
///
/// The returned samples are interleaved (L,R,L,R,... for stereo).
///
/// If an event producer is provided, progress events will be sent
/// after each chunk with (frames_rendered, total_frames).
pub fn render_to_memory(
project: &mut Project,
pool: &AudioPool,
settings: &ExportSettings,
mut event_tx: Option<&mut rtrb::Producer<AudioEvent>>,
) -> Result<Vec<f32>, String>
{
// Calculate total number of frames
let duration = settings.end_time - settings.start_time;
let total_frames = (duration.seconds_to_f64() * settings.sample_rate as f64).round() as usize;
let total_samples = total_frames * settings.channels as usize;
println!("Export: duration={:.3}s, total_frames={}, total_samples={}, channels={}",
duration.seconds_to_f64(), total_frames, total_samples, settings.channels);
let chunk_samples = EXPORT_CHUNK_FRAMES * settings.channels as usize;
// Create buffer for rendering
let mut render_buffer = vec![0.0f32; chunk_samples];
let mut buffer_pool = BufferPool::new(16, chunk_samples);
// Collect all rendered samples
let mut all_samples = Vec::with_capacity(total_samples);
let mut playhead = settings.start_time;
let chunk_duration = EXPORT_CHUNK_FRAMES as f64 / settings.sample_rate as f64;
let mut frames_rendered = 0;
// Render the entire timeline in chunks
while playhead < settings.end_time {
// Clear the render buffer
render_buffer.fill(0.0);
// Render this chunk
project.render(
&mut render_buffer,
pool,
&mut buffer_pool,
playhead,
&settings.tempo_map,
settings.sample_rate,
settings.channels,
false,
None, // export never runs with a recording in flight
);
// Calculate how many samples we actually need from this chunk
let remaining_time = settings.end_time - playhead;
let samples_needed = if remaining_time.seconds_to_f64() < chunk_duration {
// Calculate frames needed and ensure it's a whole number
let frames_needed = (remaining_time.seconds_to_f64() * settings.sample_rate as f64).round() as usize;
let samples = frames_needed * settings.channels as usize;
// Ensure we don't exceed chunk size
samples.min(chunk_samples)
} else {
chunk_samples
};
// Append to output
all_samples.extend_from_slice(&render_buffer[..samples_needed]);
// Update progress
frames_rendered += samples_needed / settings.channels as usize;
if let Some(event_tx) = event_tx.as_mut() {
let _ = event_tx.push(AudioEvent::ExportProgress {
frames_rendered,
total_frames,
});
}
playhead = playhead + Seconds(chunk_duration);
}
println!("Export: rendered {} samples total", all_samples.len());
// Verify the sample count is a multiple of channels
if all_samples.len() % settings.channels as usize != 0 {
return Err(format!(
"Sample count {} is not a multiple of channel count {}",
all_samples.len(),
settings.channels
));
}
Ok(all_samples)
}
/// Write WAV file using hound
fn write_wav<P: AsRef<Path>>(
samples: &[f32],
settings: &ExportSettings,
output_path: P,
) -> Result<(), String> {
let spec = hound::WavSpec {
channels: settings.channels as u16,
sample_rate: settings.sample_rate,
bits_per_sample: settings.bit_depth,
sample_format: hound::SampleFormat::Int,
};
let mut writer = hound::WavWriter::create(output_path, spec)
.map_err(|e| format!("Failed to create WAV file: {}", e))?;
// Write samples
match settings.bit_depth {
16 => {
for &sample in samples {
let clamped = sample.max(-1.0).min(1.0);
let pcm_value = (clamped * 32767.0) as i16;
writer.write_sample(pcm_value)
.map_err(|e| format!("Failed to write sample: {}", e))?;
}
}
24 => {
for &sample in samples {
let clamped = sample.max(-1.0).min(1.0);
let pcm_value = (clamped * 8388607.0) as i32;
writer.write_sample(pcm_value)
.map_err(|e| format!("Failed to write sample: {}", e))?;
}
}
_ => return Err(format!("Unsupported bit depth: {}", settings.bit_depth)),
}
writer.finalize()
.map_err(|e| format!("Failed to finalize WAV file: {}", e))?;
Ok(())
}
/// Export real FLAC via ffmpeg from already-rendered interleaved f32 samples (Vorbis-comment
/// metadata). Replaces the former `write_flac`, which wrote WAV bytes to a `.flac` file. 16-bit
/// uses S16; 24-bit uses S32 (ffmpeg's flac encoder emits `bits_per_raw_sample = 24` for S32,
/// taking the top 24 bits).
fn export_flac<P: AsRef<Path>>(
samples: &[f32],
settings: &ExportSettings,
output_path: P,
) -> Result<(), String> {
use ffmpeg_next as ffmpeg;
ffmpeg::init().map_err(|e| format!("Failed to initialize FFmpeg: {}", e))?;
let codec = ffmpeg::encoder::find(ffmpeg::codec::Id::FLAC)
.ok_or("FLAC encoder not found in this ffmpeg build")?;
let mut output = ffmpeg::format::output(&output_path)
.map_err(|e| format!("Failed to create output file: {}", e))?;
let channel_layout = match settings.channels {
1 => ffmpeg::channel_layout::ChannelLayout::MONO,
2 => ffmpeg::channel_layout::ChannelLayout::STEREO,
_ => return Err(format!("Unsupported channel count: {}", settings.channels)),
};
// FLAC accepts packed S16 or S32; S32 → 24-bit output.
let use_24 = settings.bit_depth >= 24;
let sample_fmt = if use_24 {
ffmpeg::format::Sample::I32(ffmpeg::format::sample::Type::Packed)
} else {
ffmpeg::format::Sample::I16(ffmpeg::format::sample::Type::Packed)
};
let mut encoder = ffmpeg::codec::Context::new_with_codec(codec)
.encoder()
.audio()
.map_err(|e| format!("Failed to create FLAC encoder: {}", e))?;
encoder.set_rate(settings.sample_rate as i32);
encoder.set_channel_layout(channel_layout);
encoder.set_format(sample_fmt);
encoder.set_time_base(ffmpeg::Rational(1, settings.sample_rate as i32));
let mut encoder = encoder.open_as(codec)
.map_err(|e| format!("Failed to open FLAC encoder: {}", e))?;
{
let mut stream = output.add_stream(codec)
.map_err(|e| format!("Failed to add stream: {}", e))?;
stream.set_parameters(&encoder);
}
apply_metadata(&mut output, &settings.metadata);
output.write_header()
.map_err(|e| format!("Failed to write FLAC header: {}", e))?;
let channels = settings.channels as usize;
let num_frames = samples.len() / channels;
let frame_size = if encoder.frame_size() > 0 { encoder.frame_size() as usize } else { 4096 };
let mut done = 0usize;
while done < num_frames {
let n = (num_frames - done).min(frame_size);
let mut frame = ffmpeg::frame::Audio::new(sample_fmt, n, channel_layout);
frame.set_rate(settings.sample_rate);
frame.set_pts(Some(done as i64)); // samples; the FLAC muxer requires PTS
let buf = frame.data_mut(0); // packed interleaved → plane 0
let base = done * channels;
if use_24 {
for i in 0..n * channels {
let s = samples[base + i].clamp(-1.0, 1.0);
let v = (s as f64 * 2_147_483_647.0) as i32; // full-scale S32; encoder takes top 24
buf[i * 4..i * 4 + 4].copy_from_slice(&v.to_le_bytes());
}
} else {
for i in 0..n * channels {
let s = samples[base + i].clamp(-1.0, 1.0);
let v = (s * 32767.0) as i16;
buf[i * 2..i * 2 + 2].copy_from_slice(&v.to_le_bytes());
}
}
encoder.send_frame(&frame).map_err(|e| format!("Failed to send FLAC frame: {}", e))?;
flac_write_packets(&mut encoder, &mut output)?;
done += n;
}
encoder.send_eof().map_err(|e| format!("Failed to flush FLAC encoder: {}", e))?;
flac_write_packets(&mut encoder, &mut output)?;
output.write_trailer().map_err(|e| format!("Failed to finalize FLAC: {}", e))?;
Ok(())
}
/// Drain encoded FLAC packets and write them (non-interleaved). Skips the trailing empty flush
/// packet, which the FLAC muxer otherwise rejects as "Invalid data". Rescales packet ts from the
/// encoder time base to the stream's.
fn flac_write_packets(
encoder: &mut ffmpeg_next::encoder::Audio,
output: &mut ffmpeg_next::format::context::Output,
) -> Result<(), String> {
let mut pkt = ffmpeg_next::Packet::empty();
let enc_tb = encoder.time_base();
let stream_tb = output.stream(0).map(|s| s.time_base()).unwrap_or(enc_tb);
while encoder.receive_packet(&mut pkt).is_ok() {
if pkt.size() == 0 {
continue;
}
pkt.set_stream(0);
pkt.rescale_ts(enc_tb, stream_tb);
pkt.write(output).map_err(|e| format!("Failed to write FLAC packet: {}", e))?;
}
Ok(())
}
/// Append a RIFF `LIST`/`INFO` metadata chunk to a finished WAV file (hound writes no tags), then
/// fix up the top-level RIFF size. Maps ffmpeg-style keys to RIFF INFO sub-chunk IDs. Trailing INFO
/// chunks are ignored by players that don't read them.
fn append_wav_info_chunk(path: &Path, metadata: &[(String, String)]) -> Result<(), String> {
use std::io::{Seek, SeekFrom, Write};
let riff_id = |key: &str| -> Option<&'static [u8; 4]> {
match key {
"title" => Some(b"INAM"),
"artist" => Some(b"IART"),
"album" => Some(b"IPRD"),
"genre" => Some(b"IGNR"),
"comment" => Some(b"ICMT"),
"date" => Some(b"ICRD"),
"track" => Some(b"ITRK"),
_ => None,
}
};
let mut info: Vec<u8> = Vec::new();
info.extend_from_slice(b"INFO");
for (key, val) in metadata {
if val.is_empty() {
continue;
}
let Some(id) = riff_id(key) else { continue };
let mut bytes = val.as_bytes().to_vec();
bytes.push(0); // NUL-terminate
if bytes.len() % 2 == 1 {
bytes.push(0); // pad to even
}
info.extend_from_slice(id);
info.extend_from_slice(&(bytes.len() as u32).to_le_bytes());
info.extend_from_slice(&bytes);
}
if info.len() <= 4 {
return Ok(()); // nothing but the "INFO" tag
}
let mut list: Vec<u8> = Vec::with_capacity(info.len() + 8);
list.extend_from_slice(b"LIST");
list.extend_from_slice(&(info.len() as u32).to_le_bytes());
list.extend_from_slice(&info);
let mut f = std::fs::OpenOptions::new()
.read(true)
.write(true)
.open(path)
.map_err(|e| format!("Failed to open WAV for tagging: {}", e))?;
let end = f.seek(SeekFrom::End(0)).map_err(|e| e.to_string())?;
if end % 2 == 1 {
f.write_all(&[0]).map_err(|e| e.to_string())?;
}
f.write_all(&list).map_err(|e| format!("Failed to write WAV tags: {}", e))?;
let new_len = f.seek(SeekFrom::End(0)).map_err(|e| e.to_string())?;
f.seek(SeekFrom::Start(4)).map_err(|e| e.to_string())?;
f.write_all(&((new_len - 8) as u32).to_le_bytes())
.map_err(|e| format!("Failed to update RIFF size: {}", e))?;
Ok(())
}
/// Export audio as MP3 using FFmpeg (streaming - render and encode simultaneously)
fn export_mp3<P: AsRef<Path>>(
project: &mut Project,
pool: &AudioPool,
settings: &ExportSettings,
output_path: P,
mut event_tx: Option<&mut rtrb::Producer<AudioEvent>>,
) -> Result<(), String> {
// Initialize FFmpeg
ffmpeg_next::init().map_err(|e| format!("Failed to initialize FFmpeg: {}", e))?;
// Set up FFmpeg encoder
let encoder_codec = ffmpeg_next::encoder::find(ffmpeg_next::codec::Id::MP3)
.ok_or("MP3 encoder (libmp3lame) not found")?;
let mut output = ffmpeg_next::format::output(&output_path)
.map_err(|e| format!("Failed to create output file: {}", e))?;
let mut encoder = ffmpeg_next::codec::Context::new_with_codec(encoder_codec)
.encoder()
.audio()
.map_err(|e| format!("Failed to create encoder: {}", e))?;
let channel_layout = match settings.channels {
1 => ffmpeg_next::channel_layout::ChannelLayout::MONO,
2 => ffmpeg_next::channel_layout::ChannelLayout::STEREO,
_ => return Err(format!("Unsupported channel count: {}", settings.channels)),
};
encoder.set_rate(settings.sample_rate as i32);
encoder.set_channel_layout(channel_layout);
encoder.set_format(ffmpeg_next::format::Sample::I16(ffmpeg_next::format::sample::Type::Planar));
encoder.set_bit_rate((settings.mp3_bitrate * 1000) as usize);
encoder.set_time_base(ffmpeg_next::Rational(1, settings.sample_rate as i32));
let mut encoder = encoder.open_as(encoder_codec)
.map_err(|e| format!("Failed to open MP3 encoder: {}", e))?;
{
let mut stream = output.add_stream(encoder_codec)
.map_err(|e| format!("Failed to add stream: {}", e))?;
stream.set_parameters(&encoder);
}
apply_metadata(&mut output, &settings.metadata);
output.write_header()
.map_err(|e| format!("Failed to write header: {}", e))?;
// Calculate rendering parameters
let duration = settings.end_time - settings.start_time;
let total_frames = (duration.seconds_to_f64() * settings.sample_rate as f64).round() as usize;
let chunk_samples = EXPORT_CHUNK_FRAMES * settings.channels as usize;
let chunk_duration = EXPORT_CHUNK_FRAMES as f64 / settings.sample_rate as f64;
// Create buffers for rendering
let mut render_buffer = vec![0.0f32; chunk_samples];
let mut buffer_pool = BufferPool::new(16, chunk_samples);
// Get encoder frame size for proper buffering
let encoder_frame_size = encoder.frame_size() as usize;
let encoder_frame_size = if encoder_frame_size > 0 {
encoder_frame_size
} else {
1152 // Default MP3 frame size
};
// Sample buffer to accumulate samples until we have complete frames
let mut sample_buffer: Vec<f32> = Vec::new();
// PTS (presentation timestamp) tracking for proper timing
let mut pts: i64 = 0;
// Streaming render and encode loop
let mut playhead = settings.start_time;
let mut frames_rendered = 0;
while playhead < settings.end_time {
// Render this chunk
render_buffer.fill(0.0);
project.render(
&mut render_buffer,
pool,
&mut buffer_pool,
playhead,
&settings.tempo_map,
settings.sample_rate,
settings.channels,
false,
None, // export never runs with a recording in flight
);
// Calculate how many samples we need from this chunk
let remaining_time = settings.end_time - playhead;
let samples_needed = if remaining_time.seconds_to_f64() < chunk_duration {
((remaining_time.seconds_to_f64() * settings.sample_rate as f64) as usize * settings.channels as usize)
.min(chunk_samples)
} else {
chunk_samples
};
// Add to sample buffer
sample_buffer.extend_from_slice(&render_buffer[..samples_needed]);
// Encode complete frames from buffer
let encoder_frame_samples = encoder_frame_size * settings.channels as usize;
while sample_buffer.len() >= encoder_frame_samples {
// Extract one complete frame
let frame_samples: Vec<f32> = sample_buffer.drain(..encoder_frame_samples).collect();
// Convert to planar i16
let planar_i16 = convert_chunk_to_planar_i16(&frame_samples, settings.channels);
// Encode this frame
encode_complete_frame_mp3(
&mut encoder,
&mut output,
&planar_i16,
encoder_frame_size,
settings.sample_rate,
channel_layout,
pts,
)?;
frames_rendered += encoder_frame_size;
pts += encoder_frame_size as i64;
// Report progress
if let Some(ref mut tx) = event_tx {
let _ = tx.push(AudioEvent::ExportProgress {
frames_rendered,
total_frames,
});
}
}
playhead = playhead + Seconds(chunk_duration);
}
// Encode any remaining samples as the final frame
if !sample_buffer.is_empty() {
let planar_i16 = convert_chunk_to_planar_i16(&sample_buffer, settings.channels);
let final_frame_size = sample_buffer.len() / settings.channels as usize;
encode_complete_frame_mp3(
&mut encoder,
&mut output,
&planar_i16,
final_frame_size,
settings.sample_rate,
channel_layout,
pts,
)?;
}
// Signal that rendering is done and we're now flushing/finalizing
if let Some(ref mut tx) = event_tx {
let _ = tx.push(AudioEvent::ExportFinalizing);
}
// Flush encoder
encoder.send_eof()
.map_err(|e| format!("Failed to send EOF: {}", e))?;
receive_and_write_packets(&mut encoder, &mut output)?;
output.write_trailer()
.map_err(|e| format!("Failed to write trailer: {}", e))?;
Ok(())
}
/// Export audio as AAC using FFmpeg (streaming - render and encode simultaneously)
fn export_aac<P: AsRef<Path>>(
project: &mut Project,
pool: &AudioPool,
settings: &ExportSettings,
output_path: P,
mut event_tx: Option<&mut rtrb::Producer<AudioEvent>>,
) -> Result<(), String> {
// Initialize FFmpeg
ffmpeg_next::init().map_err(|e| format!("Failed to initialize FFmpeg: {}", e))?;
// Set up FFmpeg encoder
let encoder_codec = ffmpeg_next::encoder::find(ffmpeg_next::codec::Id::AAC)
.ok_or("AAC encoder not found")?;
let mut output = ffmpeg_next::format::output(&output_path)
.map_err(|e| format!("Failed to create output file: {}", e))?;
let mut encoder = ffmpeg_next::codec::Context::new_with_codec(encoder_codec)
.encoder()
.audio()
.map_err(|e| format!("Failed to create encoder: {}", e))?;
let channel_layout = match settings.channels {
1 => ffmpeg_next::channel_layout::ChannelLayout::MONO,
2 => ffmpeg_next::channel_layout::ChannelLayout::STEREO,
_ => return Err(format!("Unsupported channel count: {}", settings.channels)),
};
encoder.set_rate(settings.sample_rate as i32);
encoder.set_channel_layout(channel_layout);
encoder.set_format(ffmpeg_next::format::Sample::F32(ffmpeg_next::format::sample::Type::Planar));
encoder.set_bit_rate((settings.mp3_bitrate * 1000) as usize);
encoder.set_time_base(ffmpeg_next::Rational(1, settings.sample_rate as i32));
let mut encoder = encoder.open_as(encoder_codec)
.map_err(|e| format!("Failed to open AAC encoder: {}", e))?;
{
let mut stream = output.add_stream(encoder_codec)
.map_err(|e| format!("Failed to add stream: {}", e))?;
stream.set_parameters(&encoder);
}
apply_metadata(&mut output, &settings.metadata);
output.write_header()
.map_err(|e| format!("Failed to write header: {}", e))?;
// Calculate rendering parameters
let duration = settings.end_time - settings.start_time;
let total_frames = (duration.seconds_to_f64() * settings.sample_rate as f64).round() as usize;
let chunk_samples = EXPORT_CHUNK_FRAMES * settings.channels as usize;
let chunk_duration = EXPORT_CHUNK_FRAMES as f64 / settings.sample_rate as f64;
// Create buffers for rendering
let mut render_buffer = vec![0.0f32; chunk_samples];
let mut buffer_pool = BufferPool::new(16, chunk_samples);
// Get encoder frame size for proper buffering
let encoder_frame_size = encoder.frame_size() as usize;
let encoder_frame_size = if encoder_frame_size > 0 {
encoder_frame_size
} else {
1024 // Default AAC frame size
};
// Sample buffer to accumulate samples until we have complete frames
let mut sample_buffer: Vec<f32> = Vec::new();
// PTS (presentation timestamp) tracking for proper timing
let mut pts: i64 = 0;
// Streaming render and encode loop
let mut playhead = settings.start_time;
let mut frames_rendered = 0;
while playhead < settings.end_time {
// Render this chunk
render_buffer.fill(0.0);
project.render(
&mut render_buffer,
pool,
&mut buffer_pool,
playhead,
&settings.tempo_map,
settings.sample_rate,
settings.channels,
false,
None, // export never runs with a recording in flight
);
// Calculate how many samples we need from this chunk
let remaining_time = settings.end_time - playhead;
let samples_needed = if remaining_time.seconds_to_f64() < chunk_duration {
((remaining_time.seconds_to_f64() * settings.sample_rate as f64) as usize * settings.channels as usize)
.min(chunk_samples)
} else {
chunk_samples
};
// Add to sample buffer
sample_buffer.extend_from_slice(&render_buffer[..samples_needed]);
// Encode complete frames from buffer
let encoder_frame_samples = encoder_frame_size * settings.channels as usize;
while sample_buffer.len() >= encoder_frame_samples {
// Extract one complete frame
let frame_samples: Vec<f32> = sample_buffer.drain(..encoder_frame_samples).collect();
// Convert to planar f32
let planar_f32 = convert_chunk_to_planar_f32(&frame_samples, settings.channels);
// Encode this frame
encode_complete_frame_aac(
&mut encoder,
&mut output,
&planar_f32,
encoder_frame_size,
settings.sample_rate,
channel_layout,
pts,
)?;
frames_rendered += encoder_frame_size;
pts += encoder_frame_size as i64;
// Report progress
if let Some(ref mut tx) = event_tx {
let _ = tx.push(AudioEvent::ExportProgress {
frames_rendered,
total_frames,
});
}
}
playhead = playhead + Seconds(chunk_duration);
}
// Encode any remaining samples as the final frame
if !sample_buffer.is_empty() {
let planar_f32 = convert_chunk_to_planar_f32(&sample_buffer, settings.channels);
let final_frame_size = sample_buffer.len() / settings.channels as usize;
encode_complete_frame_aac(
&mut encoder,
&mut output,
&planar_f32,
final_frame_size,
settings.sample_rate,
channel_layout,
pts,
)?;
}
// Signal that rendering is done and we're now flushing/finalizing
if let Some(ref mut tx) = event_tx {
let _ = tx.push(AudioEvent::ExportFinalizing);
}
// Flush encoder
encoder.send_eof()
.map_err(|e| format!("Failed to send EOF: {}", e))?;
receive_and_write_packets(&mut encoder, &mut output)?;
output.write_trailer()
.map_err(|e| format!("Failed to write trailer: {}", e))?;
Ok(())
}
/// Convert a chunk of interleaved f32 samples to planar i16 format
fn convert_chunk_to_planar_i16(interleaved: &[f32], channels: u32) -> Vec<Vec<i16>> {
let num_frames = interleaved.len() / channels as usize;
let mut planar = vec![vec![0i16; num_frames]; channels as usize];
for (i, chunk) in interleaved.chunks(channels as usize).enumerate() {
for (ch, &sample) in chunk.iter().enumerate() {
let clamped = sample.max(-1.0).min(1.0);
planar[ch][i] = (clamped * 32767.0) as i16;
}
}
planar
}
/// Convert a chunk of interleaved f32 samples to planar f32 format.
///
/// Non-finite samples (NaN/±Inf) are replaced with `0.0` and finite samples are
/// clamped to `[-1.0, 1.0]`: the float encoders (e.g. AAC, which takes `fltp`)
/// reject a frame outright on "(near) NaN/+-Inf", failing the whole export, so we
/// sanitize here exactly as the integer paths already clamp.
fn convert_chunk_to_planar_f32(interleaved: &[f32], channels: u32) -> Vec<Vec<f32>> {
let num_frames = interleaved.len() / channels as usize;
let mut planar = vec![vec![0.0f32; num_frames]; channels as usize];
let mut non_finite = 0u64;
for (i, chunk) in interleaved.chunks(channels as usize).enumerate() {
for (ch, &sample) in chunk.iter().enumerate() {
planar[ch][i] = if sample.is_finite() {
sample.clamp(-1.0, 1.0)
} else {
non_finite += 1;
0.0
};
}
}
if non_finite > 0 {
// One-time warning: we sanitized rather than failed, but a non-finite
// sample reaching here means something upstream (an effect, automation,
// or a source decode) produced NaN/Inf — worth chasing if audio is wrong.
use std::sync::atomic::{AtomicBool, Ordering};
static WARNED: AtomicBool = AtomicBool::new(false);
if !WARNED.swap(true, Ordering::Relaxed) {
eprintln!(
"⚠️ [EXPORT] sanitized {} non-finite (NaN/Inf) audio sample(s) in a chunk — \
check effects/automation/source decode",
non_finite
);
}
}
planar
}
/// Encode a single complete frame of planar i16 samples to MP3
fn encode_complete_frame_mp3(
encoder: &mut ffmpeg_next::encoder::Audio,
output: &mut ffmpeg_next::format::context::Output,
planar_samples: &[Vec<i16>],
num_frames: usize,
sample_rate: u32,
channel_layout: ffmpeg_next::channel_layout::ChannelLayout,
pts: i64,
) -> Result<(), String> {
if num_frames == 0 {
return Ok(());
}
let channels = planar_samples.len();
// Create audio frame
let mut frame = ffmpeg_next::frame::Audio::new(
ffmpeg_next::format::Sample::I16(ffmpeg_next::format::sample::Type::Planar),
num_frames,
channel_layout,
);
frame.set_rate(sample_rate);
frame.set_pts(Some(pts));
// Verify frame was allocated (check linesize[0] via planes())
if frame.planes() == 0 {
return Err("FFmpeg failed to allocate audio frame. Try exporting as WAV instead.".to_string());
}
// Copy all planar samples to frame
// Use plane_mut::<i16> instead of data_mut — data_mut(ch) is buggy for planar audio:
// FFmpeg only sets linesize[0], so data_mut returns 0-length slices for ch > 0.
// plane_mut uses self.samples() for the length, which is correct for all planes.
for ch in 0..channels {
let plane = frame.plane_mut::<i16>(ch);
plane.copy_from_slice(&planar_samples[ch]);
}
encoder.send_frame(&frame)
.map_err(|e| format!("Failed to send frame: {}", e))?;
receive_and_write_packets(encoder, output)?;
Ok(())
}
/// Encode a single complete frame of planar f32 samples to AAC
fn encode_complete_frame_aac(
encoder: &mut ffmpeg_next::encoder::Audio,
output: &mut ffmpeg_next::format::context::Output,
planar_samples: &[Vec<f32>],
num_frames: usize,
sample_rate: u32,
channel_layout: ffmpeg_next::channel_layout::ChannelLayout,
pts: i64,
) -> Result<(), String> {
if num_frames == 0 {
return Ok(());
}
let channels = planar_samples.len();
// Create audio frame
let mut frame = ffmpeg_next::frame::Audio::new(
ffmpeg_next::format::Sample::F32(ffmpeg_next::format::sample::Type::Planar),
num_frames,
channel_layout,
);
frame.set_rate(sample_rate);
frame.set_pts(Some(pts));
// Verify frame was allocated
if frame.planes() == 0 {
return Err("FFmpeg failed to allocate audio frame. Try exporting as WAV instead.".to_string());
}
// Copy all planar samples to frame
// Use plane_mut::<f32> instead of data_mut — data_mut(ch) is buggy for planar audio:
// FFmpeg only sets linesize[0], so data_mut returns 0-length slices for ch > 0.
// plane_mut uses self.samples() for the length, which is correct for all planes.
for ch in 0..channels {
let plane = frame.plane_mut::<f32>(ch);
plane.copy_from_slice(&planar_samples[ch]);
}
encoder.send_frame(&frame)
.map_err(|e| format!("Failed to send frame: {}", e))?;
receive_and_write_packets(encoder, output)?;
Ok(())
}
/// Receive encoded packets and write to output
fn receive_and_write_packets(
encoder: &mut ffmpeg_next::encoder::Audio,
output: &mut ffmpeg_next::format::context::Output,
) -> Result<(), String> {
let mut encoded = ffmpeg_next::Packet::empty();
while encoder.receive_packet(&mut encoded).is_ok() {
encoded.set_stream(0);
encoded.write_interleaved(output)
.map_err(|e| format!("Failed to write packet: {}", e))?;
}
Ok(())
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_export_settings_default() {
let settings = ExportSettings::default();
assert_eq!(settings.format, ExportFormat::Wav);
assert_eq!(settings.sample_rate, 44100);
assert_eq!(settings.channels, 2);
assert_eq!(settings.bit_depth, 16);
}
#[test]
fn test_format_extension() {
assert_eq!(ExportFormat::Wav.extension(), "wav");
assert_eq!(ExportFormat::Flac.extension(), "flac");
}
fn tagged_settings(format: ExportFormat) -> ExportSettings {
ExportSettings {
format,
sample_rate: 48000,
channels: 2,
bit_depth: 24,
mp3_bitrate: 192,
start_time: Seconds::ZERO,
end_time: Seconds(0.2), // tiny render
tempo_map: TempoMap::constant(120.0),
metadata: vec![
("title".to_string(), "Test Title".to_string()),
("artist".to_string(), "Test Artist".to_string()),
],
}
}
/// FLAC export must be a real FLAC container (not WAV bytes) carrying Vorbis-comment tags.
#[test]
fn flac_export_is_real_flac_with_tags() {
let settings = tagged_settings(ExportFormat::Flac);
let mut project = Project::new(48000);
let pool = AudioPool::new();
let path = std::env::temp_dir().join("lb_be_flac_test.flac");
export_audio(&mut project, &pool, &settings, &path, None).expect("FLAC export failed");
let bytes = std::fs::read(&path).unwrap();
assert_eq!(&bytes[0..4], b"fLaC", "not real FLAC (got {:?})", &bytes[0..4]);
let s = String::from_utf8_lossy(&bytes);
assert!(s.contains("Test Title"), "title tag missing from FLAC");
assert!(s.contains("Test Artist"), "artist tag missing from FLAC");
std::fs::remove_file(&path).ok();
}
/// WAV export keeps a valid RIFF container and gains a LIST/INFO tag chunk with a fixed-up size.
#[test]
fn wav_export_has_info_chunk() {
let settings = tagged_settings(ExportFormat::Wav);
let mut project = Project::new(48000);
let pool = AudioPool::new();
let path = std::env::temp_dir().join("lb_be_wav_test.wav");
export_audio(&mut project, &pool, &settings, &path, None).expect("WAV export failed");
let bytes = std::fs::read(&path).unwrap();
assert_eq!(&bytes[0..4], b"RIFF");
assert_eq!(&bytes[8..12], b"WAVE");
let riff_size = u32::from_le_bytes([bytes[4], bytes[5], bytes[6], bytes[7]]) as usize;
assert_eq!(riff_size, bytes.len() - 8, "RIFF size not fixed up after tagging");
let s = String::from_utf8_lossy(&bytes);
assert!(s.contains("LIST") && s.contains("INFO") && s.contains("INAM"),
"no RIFF INFO chunk");
assert!(s.contains("Test Title"), "title not in WAV INFO chunk");
std::fs::remove_file(&path).ok();
}
}