chat/lib/voice_transcoder.php

<?php

function voiceTranscodingProfile(): string {
    $profile = (string)getConfigVal('voice.transcoding.profile', 'm4a_aac');
    return in_array($profile, ['m4a_aac', 'mp4_h264_aac'], true) ? $profile : 'm4a_aac';
}

function voiceFfmpegBinary(): string {
    $binary = trim((string)getConfigVal('voice.transcoding.ffmpeg_path', 'ffmpeg'));
    if ($binary === '' || preg_match('/[\x00-\x1F\x7F]/', $binary)) {
        throw new RuntimeException('The FFmpeg binary path is invalid.');
    }
    return $binary;
}

function runVoiceTranscodeCommand(array $command, int $timeoutSeconds): array {
    if (!function_exists('proc_open')) {
        return ['exit_code' => 127, 'stderr' => 'PHP proc_open is unavailable.'];
    }

    $process = @proc_open($command, [
        0 => ['pipe', 'r'],
        1 => ['pipe', 'w'],
        2 => ['pipe', 'w'],
    ], $pipes, null, null, ['bypass_shell' => true]);
    if (!is_resource($process)) {
        return ['exit_code' => 127, 'stderr' => 'FFmpeg could not be started.'];
    }

    fclose($pipes[0]);
    stream_set_blocking($pipes[1], false);
    stream_set_blocking($pipes[2], false);
    $stdout = '';
    $stderr = '';
    $started = microtime(true);
    $exitCode = -1;

    while (true) {
        $stdout .= (string)stream_get_contents($pipes[1]);
        $stderr .= (string)stream_get_contents($pipes[2]);
        $status = proc_get_status($process);
        if (!$status['running']) {
            $exitCode = (int)$status['exitcode'];
            break;
        }
        if ((microtime(true) - $started) >= $timeoutSeconds) {
            proc_terminate($process);
            usleep(100000);
            $status = proc_get_status($process);
            if ($status['running']) proc_terminate($process, 9);
            $exitCode = 124;
            $stderr .= "\nFFmpeg timed out.";
            break;
        }
        usleep(50000);
    }

    $stdout .= (string)stream_get_contents($pipes[1]);
    $stderr .= (string)stream_get_contents($pipes[2]);
    fclose($pipes[1]);
    fclose($pipes[2]);
    $closeCode = proc_close($process);
    if ($exitCode < 0) $exitCode = $closeCode;

    return [
        'exit_code' => $exitCode,
        'stdout' => substr($stdout, -4000),
        'stderr' => substr($stderr, -4000),
    ];
}

function transcodeVoiceRecording(
    string $sourcePath,
    string $sourceFilename,
    string $sourceMime
): array {
    if (!getConfigVal('voice.transcoding.enabled', false)) {
        return ['filename' => $sourceFilename, 'mime' => $sourceMime, 'transcoded' => false];
    }

    $profile = voiceTranscodingProfile();
    $bitrate = max(48, min(320, (int)getConfigVal('voice.transcoding.audio_bitrate_kbps', 128)));
    $timeout = max(5, min(300, (int)getConfigVal('voice.transcoding.timeout_seconds', 45)));
    $fallback = (bool)getConfigVal('voice.transcoding.fallback_to_source', true);
    $token = pathinfo($sourceFilename, PATHINFO_FILENAME);
    if (!preg_match('/^[a-f0-9]{40}$/', $token)) {
        throw new RuntimeException('Voice recording filename is invalid.');
    }

    $extension = $profile === 'mp4_h264_aac' ? 'mp4' : 'm4a';
    $outputMime = $profile === 'mp4_h264_aac' ? 'video/mp4' : 'audio/mp4';
    $outputFilename = $token . '.' . $extension;
    $outputPath = dirname($sourcePath) . '/' . $outputFilename;
    $temporaryPath = dirname($sourcePath) . '/.' . $token . '.tmp.' . $extension;
    $binary = voiceFfmpegBinary();

    if ($profile === 'mp4_h264_aac') {
        $command = [
            $binary, '-nostdin', '-hide_banner', '-loglevel', 'error', '-y',
            '-f', 'lavfi', '-i', 'color=c=black:s=16x16:r=1',
            '-i', $sourcePath,
            '-map', '0:v:0', '-map', '1:a:0', '-shortest',
            '-c:v', 'libx264', '-preset', 'veryfast', '-tune', 'stillimage',
            '-profile:v', 'baseline', '-level', '3.0', '-pix_fmt', 'yuv420p',
            '-c:a', 'aac', '-profile:a', 'aac_low', '-b:a', $bitrate . 'k',
            '-map_metadata', '-1', '-movflags', '+faststart', $temporaryPath,
        ];
    } else {
        $command = [
            $binary, '-nostdin', '-hide_banner', '-loglevel', 'error', '-y',
            '-i', $sourcePath, '-vn',
            '-c:a', 'aac', '-profile:a', 'aac_low', '-b:a', $bitrate . 'k',
            '-map_metadata', '-1', '-movflags', '+faststart', $temporaryPath,
        ];
    }

    $result = runVoiceTranscodeCommand($command, $timeout);
    $validOutput = $result['exit_code'] === 0
        && is_file($temporaryPath)
        && filesize($temporaryPath) > 0;
    if (!$validOutput) {
        if (is_file($temporaryPath)) @unlink($temporaryPath);
        $detail = trim((string)($result['stderr'] ?? ''));
        error_log('Voice transcoding failed: ' . ($detail !== '' ? $detail : 'unknown FFmpeg error'));
        if ($fallback) {
            return ['filename' => $sourceFilename, 'mime' => $sourceMime, 'transcoded' => false];
        }
        throw new RuntimeException('Voice transcoding failed. Check the FFmpeg dashboard settings.');
    }

    $sourceBackupPath = null;
    if ($outputPath === $sourcePath) {
        $sourceBackupPath = dirname($sourcePath) . '/.' . $token . '.source.' . $extension;
        if (!@rename($sourcePath, $sourceBackupPath)) {
            @unlink($temporaryPath);
            if ($fallback) {
                return ['filename' => $sourceFilename, 'mime' => $sourceMime, 'transcoded' => false];
            }
            throw new RuntimeException('The original voice clip could not be prepared for replacement.');
        }
    }

    if (!@rename($temporaryPath, $outputPath)) {
        @unlink($temporaryPath);
        if ($sourceBackupPath !== null && is_file($sourceBackupPath)) {
            @rename($sourceBackupPath, $sourcePath);
        }
        if ($fallback && is_file($sourcePath)) {
            return ['filename' => $sourceFilename, 'mime' => $sourceMime, 'transcoded' => false];
        }
        throw new RuntimeException('The transcoded voice clip could not be stored.');
    }

    if ($sourceBackupPath !== null) {
        @unlink($sourceBackupPath);
    } else {
        @unlink($sourcePath);
    }
    return ['filename' => $outputFilename, 'mime' => $outputMime, 'transcoded' => true];
}