prevent maindata underflow at start

and remove some unnecessary code

src/Audio.cpp

@@ -3,7 +3,7 @@
  *
  *  Created on: Oct 26.2018
  *
- *  Version 3.0.9h
+ *  Version 3.0.9i
  *  Updated on: Apr 22.2024
  *      Author: Wolle (schreibfaul1)
  *
@@ -4426,11 +4426,7 @@ int Audio::sendBytes(uint8_t* data, size_t len) {
     //                 < 0: there has been an error
 
     if(m_decodeError < 0) { // Error, skip the frame...
-                            //        i2s_zero_dma_buffer((i2s_port_t)m_i2s_num);
-        if(m_codec == CODEC_MP3 && (m_decodeError == -2)) {
-            ; // at the beginning this doesn't have to be a mistake, suppress errorcode MAINDATA_UNDERFLOW
-        }
-        else {
+
         printDecodeError(m_decodeError);
         m_f_playing = false; // seek for new syncword
         if(m_codec == CODEC_FLAC) {
@@ -4444,7 +4440,7 @@ int Audio::sendBytes(uint8_t* data, size_t len) {
             if(m_decodeError == ERR_OPUS_WIDE_BAND_UNSUPPORTED) stopSong();
             if(m_decodeError == ERR_OPUS_SUPER_WIDE_BAND_UNSUPPORTED) stopSong();
         }
-        }
+
         return 1; // skip one byte and seek for the next sync word
     }
     bytesDecoded = len - bytesLeft;

src/mp3_decoder/mp3_decoder.cpp

@@ -3,7 +3,7 @@
  * libhelix_HMP3DECODER
  *
  *  Created on: 26.10.2018
- *  Updated on: 29.03.2023
+ *  Updated on: 22.04.2023
  */
 #include "mp3_decoder.h"
 /* clip to range [-2^n, 2^n - 1] */
@@ -1382,6 +1382,7 @@ int MP3Decode( unsigned char *inbuf, int *bytesLeft, short *outbuf, int useSize)
     int offset, bitOffset, mainBits, gr, ch, fhBytes, siBytes, freeFrameBytes;
     int prevBitOffset, sfBlockBits, huffBlockBits;
     unsigned char *mainPtr;
+    static uint8_t underflowCounter = 0; // http://macslons-irish-pub-radio.stream.laut.fm/macslons-irish-pub-radio
 
     /* unpack frame header */
     fhBytes = UnpackFrameHeader(inbuf);
@@ -1444,6 +1445,7 @@ int MP3Decode( unsigned char *inbuf, int *bytesLeft, short *outbuf, int useSize)
         /* fill main data buffer with enough new data for this frame */
         if (m_MP3DecInfo->mainDataBytes >= m_MP3DecInfo->mainDataBegin) {
             /* adequate "old" main data available (i.e. bit reservoir) */
+            underflowCounter = 0;
             memmove(m_MP3DecInfo->mainBuf,
                     m_MP3DecInfo->mainBuf + m_MP3DecInfo->mainDataBytes - m_MP3DecInfo->mainDataBegin,
                     m_MP3DecInfo->mainDataBegin);
@@ -1456,10 +1458,14 @@ int MP3Decode( unsigned char *inbuf, int *bytesLeft, short *outbuf, int useSize)
             mainPtr = m_MP3DecInfo->mainBuf;
         } else {
             /* not enough data in bit reservoir from previous frames (perhaps starting in middle of file) */
+            underflowCounter ++;
             memcpy(m_MP3DecInfo->mainBuf + m_MP3DecInfo->mainDataBytes, inbuf, m_MP3DecInfo->nSlots);
             m_MP3DecInfo->mainDataBytes += m_MP3DecInfo->nSlots;
             inbuf += m_MP3DecInfo->nSlots;
             *bytesLeft -= (m_MP3DecInfo->nSlots);
+            if(underflowCounter < 4){
+                return ERR_MP3_NONE;
+            }
             MP3ClearBadFrame( outbuf);
             return ERR_MP3_MAINDATA_UNDERFLOW;
         }