ncm: FLAC 解码落地(dr_flac 0.13.4 单头入库) + 缓存键=歌曲ID+音质档位

- 解码分发 decoder.c：magic(fLaC→dr_flac / 其它→minimp3)；flac ≤16bit→S16、 >16bit→S32 满幅送 audiod(AUDIO_FMT_S32)，rate/ch/bits 按实际流，零 SRC 零裁剪 - song_url_auto 接受 flac（type 权威/url 扩展名兜底），降级语义不变；flac 下载限幅 1GB - 缓存键 song_<id>_<level>.<ext>：同歌同档命中不重下，换档新条目旧档留 LRU； ext 前导点正名(修双点名)，lookup 回退历史双点名+旧无档键温和兼容 - audio_out S32 通路（AUDIOD/ALSA/WAV）+ 流死重开按 bits 还原格式 - 验证(0 真实请求)：44.1k/16 与 96k/24 自制样本宿主+qemu 帧数/时长精确、逐样本零误差；mp3 回归逐帧一致；player_flow_sim P1-P6(新 P6 档位键/flac ext)、 cache_evict/cover/pagination/window/audiod_chain sim 全 PASS；mipsel 0 warning - REPORT §19 / VENDOR_NOTES dr_flac 条目；未部署真机（留主会话）
2026-09-01 14:14:38 +08:00
1 parent 80bc191593
commit 70aec677ce
@@ -0,0 +1,141 @@
+/* play/decoder.c — 格式分发解码实现（接口见 decoder.h，REPORT §19）。
+ *
+ * mp3 细节：minimp3_ex 的 dec.info（hz/channels）在首次 mp3dec_ex_read 后才保证有效，
+ * 而调用方开 audio_out 前就要 rate/ch —— open 时先预读一批进 stash，read 先吐 stash。
+ * seek(mp3)：关+重开（MP3D_SEEK_TO_BYTE 索引在 open 时重建）再按字节近似 seek，同旧语义。
+ */
+#include "decoder.h"
+#include "minimp3_ex.h"
+#include "dr_flac.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define DEC_STASH_FRAMES 4096            /* open 预读上限（帧），与播放循环单块读同量级 */
+
+enum { DEC_MP3 = 0, DEC_FLAC = 1 };
+
+struct ncm_decoder {
+    int      kind;
+    char     path[512];
+    int      rate, ch, bits;
+    int64_t  total_frames;               /* 0=未知 */
+    /* mp3 */
+    mp3dec_ex_t mp3;
+    int16_t  *stash;                     /* 预读样本（交织 s16），stash_n 个样本 */
+    size_t    stash_n, stash_off;
+    /* flac */
+    drflac   *flac;
+};
+
+/* magic 探测：首 4 字节 "fLaC" → flac；其余（ID3 / 0xFF 帧同步 / 未知）→ mp3
+ *（未知格式留给 minimp3 在 open 时报错，不在本层加第三种分支）。 */
+static int sniff_kind(const char *path)
+{
+    unsigned char m[4] = {0};
+    FILE *f = fopen(path, "rb");
+    if (f) { size_t n = fread(m, 1, 4, f); fclose(f); if (n < 4) return DEC_MP3; }
+    if (m[0] == 'f' && m[1] == 'L' && m[2] == 'a' && m[3] == 'C') return DEC_FLAC;
+    return DEC_MP3;
+}
+
+int ncm_dec_open(ncm_decoder_t **out, const char *path,
+                 int *rate, int *ch, int *bits, int64_t *total_frames)
+{
+    if (!out || !path) return -1;
+    ncm_decoder_t *d = (ncm_decoder_t *)calloc(1, sizeof *d);
+    if (!d) return -1;
+    d->kind = sniff_kind(path);
+    snprintf(d->path, sizeof d->path, "%s", path);
+
+    if (d->kind == DEC_FLAC) {
+        d->flac = drflac_open_file(path, NULL);
+        if (!d->flac) { free(d); return -1; }
+        d->rate = (int)d->flac->sampleRate;
+        d->ch   = (int)d->flac->channels;
+        /* 位宽映射（AUDIOD §4 归一交给 SDK/audiod）：≤16 → S16；>16 → S32 满幅 */
+        d->bits = (d->flac->bitsPerSample <= 16) ? 16 : 32;
+        d->total_frames = (int64_t)d->flac->totalPCMFrameCount;
+    } else {
+        if (mp3dec_ex_open(&d->mp3, path, MP3D_SEEK_TO_BYTE) != 0) { free(d); return -1; }
+        d->bits = 16;
+        d->stash = (int16_t *)malloc(DEC_STASH_FRAMES * 2 * sizeof(int16_t));
+        if (!d->stash) { mp3dec_ex_close(&d->mp3); free(d); return -1; }
+        /* 预读首块：填 dec.info（hz/channels）+ 预热 stash */
+        size_t got = mp3dec_ex_read(&d->mp3, d->stash, DEC_STASH_FRAMES * 2);
+        d->stash_n = got;
+        d->rate = d->mp3.info.hz;
+        d->ch   = d->mp3.info.channels;
+        if (d->rate <= 0 || d->ch <= 0) {           /* 首块即失败/空流 */
+            mp3dec_ex_close(&d->mp3); free(d->stash); free(d); return -1;
+        }
+        d->total_frames = (d->ch > 0) ? (int64_t)(d->mp3.samples / (uint64_t)d->ch) : 0;
+    }
+
+    if (d->ch < 1 || d->ch > 2) { ncm_dec_close(d); return -1; }   /* v1 只接 单/双声道 */
+    *out = d;
+    if (rate) *rate = d->rate;
+    if (ch)   *ch   = d->ch;
+    if (bits) *bits = d->bits;
+    if (total_frames) *total_frames = d->total_frames;
+    return 0;
+}
+
+int64_t ncm_dec_read(ncm_decoder_t *d, void *buf, int64_t cap_frames)
+{
+    if (!d || !buf || cap_frames <= 0) return 0;
+    if (d->kind == DEC_FLAC) {
+        if (d->bits == 16)
+            return (int64_t)drflac_read_pcm_frames_s16(d->flac, (drflac_uint64)cap_frames,
+                                                       (drflac_int16 *)buf);
+        return (int64_t)drflac_read_pcm_frames_s32(d->flac, (drflac_uint64)cap_frames,
+                                                   (drflac_int32 *)buf);
+    }
+    /* mp3：先吐 stash，再直读 */
+    int16_t *out = (int16_t *)buf;
+    int64_t cap_samples = cap_frames * d->ch;
+    int64_t done = 0;
+    if (d->stash_off < d->stash_n) {
+        size_t left = d->stash_n - d->stash_off;
+        size_t take = left < (size_t)cap_samples ? left : (size_t)cap_samples;
+        memcpy(out, d->stash + d->stash_off, take * sizeof(int16_t));
+        d->stash_off += take;
+        done += (int64_t)take;
+    }
+    if (done < cap_samples) {
+        size_t got = mp3dec_ex_read(&d->mp3, out + done, (size_t)(cap_samples - done));
+        done += (int64_t)got;
+    }
+    return done / d->ch;
+}
+
+int ncm_dec_seek_ms(ncm_decoder_t *d, int64_t ms, int64_t file_bytes, int64_t dur_ms)
+{
+    if (!d || ms < 0) return -1;
+    if (d->kind == DEC_FLAC) {
+        drflac_uint64 frame = (drflac_uint64)(ms * d->rate / 1000);
+        return drflac_seek_to_pcm_frame(d->flac, frame) ? 0 : -1;
+    }
+    /* mp3：关+重开（重建字节索引）再按字节近似 */
+    mp3dec_ex_close(&d->mp3);
+    memset(&d->mp3, 0, sizeof d->mp3);
+    if (mp3dec_ex_open(&d->mp3, d->path, MP3D_SEEK_TO_BYTE) != 0) return -1;
+    d->stash_n = d->stash_off = 0;
+    int64_t target = (file_bytes > 0 && dur_ms > 0) ? file_bytes * ms / dur_ms : 0;
+    return mp3dec_ex_seek(&d->mp3, (uint64_t)(target > 0 ? target : 0));
+}
+
+void ncm_dec_close(ncm_decoder_t *d)
+{
+    if (!d) return;
+    if (d->kind == DEC_FLAC) { if (d->flac) drflac_close(d->flac); }
+    else { mp3dec_ex_close(&d->mp3); free(d->stash); }
+    free(d);
+}
+
+const char *ncm_dec_format(const ncm_decoder_t *d)
+{
+    if (!d) return "?";
+    return d->kind == DEC_FLAC ? "flac" : "mp3";
+}