Announcing MP4 audio bitrates, adjustments for MPEG-2 Layer 3 (lower …

…samplerates)

README.md

@@ -56,10 +56,10 @@ _* At the moment, only text, 24-bit and 32-bit RGB overlays are handled, matrici
 
 ### Roadmap
 
-- [ ] Alternative audio codecs
 - [ ] Assorted WebUI to handle media reconfiguration and live preview
 - [ ] Motion detection reimplementation
 - [ ] Hardware support improvement (older SoCs, general usage chips)
+- [ ] Alternative audio codecs
 
 
 ### Technical support and donations

divinus.yaml

@@ -51,7 +51,8 @@ http_post:
 
 audio:
   enable: false
-  srate: 8000
+  srate: 48000
+  bitrate: 128
 
 rtsp:
   enable: true

src/media.c

@@ -23,7 +23,10 @@ unsigned int pcmSamp;
 short pcmSrc[SHINE_MAX_SAMPLES];
 
 void *aenc_thread(void) {
-    const uint32_t mp3FrmSize = 1152;
+    const uint32_t mp3FrmSize = 
+        (app_config.audio_srate >= 32000 ? 144 : 72) *
+        (app_config.audio_bitrate * 1000) / 
+        app_config.audio_srate;
 
     while (keepRunning) {
         pthread_mutex_lock(&aencMtx);
@@ -514,7 +517,7 @@ int enable_mp4(void) {
 
         mp4_set_config(app_config.mp4_width, app_config.mp4_height, app_config.mp4_fps,
             app_config.audio_enable ? HAL_AUDCODEC_MP3 : HAL_AUDCODEC_UNSPEC, 
-            app_config.audio_srate);
+            app_config.audio_bitrate, app_config.audio_srate);
     }
 
     if (ret = bind_channel(index, app_config.mp4_fps, 0)) {

src/mp4/moov.c

@@ -20,7 +20,7 @@ enum BufError write_vmhd(struct BitBuf *ptr);
 enum BufError write_smhd(struct BitBuf *ptr);
 enum BufError write_stbl(struct BitBuf *ptr, const struct MoovInfo *moov_info, char is_audio);
 enum BufError write_stsd(struct BitBuf *ptr, const struct MoovInfo *moov_info, char is_audio);
-enum BufError write_btrt(struct BitBuf *ptr);
+enum BufError write_btrt(struct BitBuf *ptr, const struct MoovInfo *moov_info);
 enum BufError write_esds(struct BitBuf *ptr, const struct MoovInfo *moov_info);
 enum BufError write_mp4a(struct BitBuf *ptr, const struct MoovInfo *moov_info);
 enum BufError write_avc1_hev1(struct BitBuf *ptr, const struct MoovInfo *moov_info);
@@ -541,7 +541,7 @@ enum BufError write_stsd(struct BitBuf *ptr, const struct MoovInfo *moov_info, c
     return BUF_OK;
 }
 
-enum BufError write_btrt(struct BitBuf *ptr) {
+enum BufError write_btrt(struct BitBuf *ptr, const struct MoovInfo *moov_info) {
     enum BufError err;
     uint32_t start_atom = ptr->offset;
     err = put_u32_be(ptr, 0);
@@ -551,9 +551,9 @@ enum BufError write_btrt(struct BitBuf *ptr) {
     chk_err;
     err = put_u32_be(ptr, 0);
     chk_err; // 4 Buffer size
-    err = put_u32_be(ptr, 25636);
+    err = put_u32_be(ptr, moov_info->audio_bitrate * 1000);
     chk_err; // 4 Max bitrate
-    err = put_u32_be(ptr, 25636);
+    err = put_u32_be(ptr, moov_info->audio_bitrate * 1000);
     chk_err; // 4 Avg bitrate
     err = put_u32_be_to_offset(ptr, start_atom, ptr->offset - start_atom);
     chk_err;
@@ -617,9 +617,9 @@ enum BufError write_DecoderConfig(struct BitBuf *ptr, const struct MoovInfo *moo
     chk_err; // streamType
     err = put_skip(ptr, 3);
     chk_err; // 3 bufferSize
-    err = put_u32_be(ptr, 128000);
+    err = put_u32_be(ptr, moov_info->audio_bitrate * 1000);
     chk_err; // 4 Max bitrate
-    err = put_u32_be(ptr, 128000);
+    err = put_u32_be(ptr, moov_info->audio_bitrate * 1000);
     chk_err; // 4 Avg bitrate
     err = put_u32_le_to_offset(ptr, var_len, varint32(ptr->offset - var_len - 4));
     chk_err;
@@ -780,7 +780,7 @@ enum BufError write_mp4a(struct BitBuf *ptr, const struct MoovInfo *moov_info) {
     chk_err; // 2 reserved
     err = write_esds(ptr, moov_info);
     chk_err;
-    err = write_btrt(ptr);
+    err = write_btrt(ptr, moov_info);
     chk_err;
     err = put_u32_be_to_offset(ptr, start_atom, ptr->offset - start_atom);
     chk_err;

src/mp4/moov.h

@@ -4,6 +4,7 @@
 
 struct MoovInfo {
     char audio_codec;
+    unsigned short audio_bitrate;
     unsigned int audio_samplerate;
     char is_h265;
     uint8_t profile_idc;

src/mp4/mp4.c

@@ -7,6 +7,7 @@
 uint32_t default_sample_size = 40000;
 
 unsigned int aud_samplerate = 0;
+unsigned short aud_bitrate = 0;
 short vid_width = 1920, vid_height = 1080;
 char aud_codec = 0, vid_framerate = 30;
 
@@ -58,12 +59,13 @@ enum BufError create_header(char is_h265) {
     chk_err return BUF_OK;
 }
 
-void mp4_set_config(short width, short height, char framerate, char acodec, int srate)
-{
+void mp4_set_config(short width, short height, char framerate,
+    char acodec, unsigned short bitrate, unsigned int srate) {
     vid_width = width;
     vid_height = height;
     vid_framerate = framerate;
     aud_codec = acodec;
+    aud_bitrate = bitrate;
     aud_samplerate = srate;
 }
 
@@ -103,7 +105,8 @@ enum BufError mp4_set_slice(const char *nal_data, const uint32_t nal_len,
     buf_moof.offset = 0;
     err = write_moof(
         &buf_moof, 0, 0, 0, default_sample_size, samples_info,
-        samples_info_len, samples_info + 1, buf_aud.offset >= 2304 ? 1 : 0);
+        samples_info_len, samples_info + 1, 
+        buf_aud.offset >= 2304 ? 1 : 0);
     chk_err;
 
     buf_mdat.offset = 0;

src/mp4/mp4.h

@@ -25,7 +25,8 @@ struct Mp4State {
     uint32_t nals_count;
 };
 
-void mp4_set_config(short width, short height, char framerate, char acodec, int srate);
+void mp4_set_config(short width, short height, char framerate,
+    char acodec, unsigned short bitrate, unsigned int srate);
 
 void mp4_set_sps(const char *nal_data, const uint32_t nal_len, char is_h265);
 void mp4_set_pps(const char *nal_data, const uint32_t nal_len, char is_h265);