C++ SampleBuffer::Allocate方法代码示例

//--Decoder stuff:
   ///Decodes the samples for this blockfile from the real file into a float buffer.
   ///This is file specific, so subclasses must implement this only.
   ///the buffer was defined like
   ///samplePtr sampleData = NewSamples(mLen, floatSample);
   ///this->ReadData(sampleData, floatSample, 0, mLen);
   ///This class should call ReadHeader() first, so it knows the length, and can prepare
   ///the file object if it needs to.
int ODFlacDecoder::Decode(SampleBuffer & data, sampleFormat & format, sampleCount start, size_t len, unsigned int channel)
{

   //we need to lock this so the target stays fixed over the seek/write callback.
   mFlacFileLock.Lock();

   bool usingCache=mLastDecodeStartSample==start;
   if(usingCache)
   {
      //we've just decoded this, so lets use a cache.  (often so for
   }


   mDecodeBufferWritePosition=0;
   mDecodeBufferLen = len;

   data.Allocate(len, mFormat);
   mDecodeBuffer = data.ptr();
   format = mFormat;

   mTargetChannel=channel;

   // Third party library has its own type alias, check it
   static_assert(sizeof(sampleCount::type) <=
                 sizeof(FLAC__int64),
                 "Type FLAC__int64 is too narrow to hold a sampleCount");
   if(!mFile->seek_absolute(static_cast<FLAC__int64>( start.as_long_long() )))
   {
      mFlacFileLock.Unlock();
      return -1;
   }

   while(mDecodeBufferWritePosition<mDecodeBufferLen)
      mFile->process_single();

   mFlacFileLock.Unlock();
   if(!usingCache)
   {
      mLastDecodeStartSample=start;
   }
   //insert into blockfile and
   //calculate summary happen in ODDecodeBlockFile::WriteODDecodeBlockFile, where this method is also called.
   return 1;
}

int ODFFmpegDecoder::Decode(SampleBuffer & data, sampleFormat & format, sampleCount start, sampleCount len, unsigned int channel)
{
   format = mScs[mStreamIndex]->m_osamplefmt;

   data.Allocate(len, format);
   samplePtr bufStart = data.ptr();
   streamContext* sc = NULL;

   // printf("start %llu len %llu\n", start, len);
   //TODO update this to work with seek - this only works linearly now.
   if(mCurrentPos > start && mCurrentPos  <= start+len + kDecodeSampleAllowance)
   {
      //this next call takes data, start and len as reference variables and updates them to reflect the NEW area that is needed.
      FillDataFromCache(bufStart, format, start,len,channel);
   }

   bool seeking = false;
   //look at the decoding timestamp and see if the next sample that will be decoded is not the next sample we need.
   if(len && (mCurrentPos > start + len  || mCurrentPos + kDecodeSampleAllowance < start ) && SeekingAllowed()) {
      sc = mScs[mStreamIndex];
      AVStream* st = sc->m_stream;
      int stindex = -1;
      uint64_t targetts;

      //printf("attempting seek to %llu\n", start);
      //we have to find the index for this stream.
      for (unsigned int i = 0; i < mFormatContext->nb_streams; i++) {
         if (mFormatContext->streams[i] == sc->m_stream )
            stindex =i;
      }

      if(stindex >=0) {
         int numAttempts = 0;
         //reset mCurrentPos to a bogus value
         mCurrentPos = start+len +1;
         while(numAttempts++ < kMaxSeekRewindAttempts && mCurrentPos > start) {
            //we want to move slightly before the start of the block file, but not too far ahead
            targetts = (start-kDecodeSampleAllowance*numAttempts/kMaxSeekRewindAttempts)  * ((double)st->time_base.den/(st->time_base.num * st->codec->sample_rate ));
            if(targetts<0)
               targetts=0;

            //printf("attempting seek to %llu, attempts %d\n", targetts, numAttempts);
            if(av_seek_frame(mFormatContext,stindex,targetts,0) >= 0){
               //find out the dts we've seekd to.
               sampleCount actualDecodeStart = 0.5 + st->codec->sample_rate * st->cur_dts  * ((double)st->time_base.num/st->time_base.den);      //this is mostly safe because den is usually 1 or low number but check for high values.

               mCurrentPos = actualDecodeStart;
               seeking = true;

               //if the seek was past our desired position, rewind a bit.
               //printf("seek ok to %llu samps, float: %f\n",actualDecodeStart,actualDecodeStartDouble);
            } else {
               printf("seek failed");
               break;
            }
         }
         if(mCurrentPos>start){
            mSeekingAllowedStatus = (bool)ODFFMPEG_SEEKING_TEST_FAILED;
            //               url_fseek(mFormatContext->pb,sc->m_pkt.pos,SEEK_SET);
            printf("seek fail, reverting to previous pos\n");
            return -1;
         }
      }
   }
   bool firstpass = true;

   //we decode up to the end of the blockfile
   while (len>0 && (mCurrentPos < start+len) && (sc = ReadNextFrame()) != NULL)
   {
      // ReadNextFrame returns 1 if stream is not to be imported
      if (sc != (streamContext*)1)
      {
         //find out the dts we've seekd to.  can't use the stream->cur_dts because it is faulty.  also note that until we do the first seek, pkt.dts can be false and will change for the same samples after the initial seek.
         sampleCount actualDecodeStart = mCurrentPos;

         // we need adjacent samples, so don't use dts most of the time which will leave gaps between frames
         // for some formats
         // The only other case for inserting silence is for initial offset and ImportFFmpeg.cpp does this for us
         if (seeking) {
            actualDecodeStart = 0.52 + (sc->m_stream->codec->sample_rate * sc->m_pkt.dts
                                        * ((double)sc->m_stream->time_base.num / sc->m_stream->time_base.den));
            //this is mostly safe because den is usually 1 or low number but check for high values.

            //hack to get rounding to work to neareset frame size since dts isn't exact
            if (sc->m_stream->codec->frame_size) {
               actualDecodeStart = ((actualDecodeStart + sc->m_stream->codec->frame_size/2) / sc->m_stream->codec->frame_size) * sc->m_stream->codec->frame_size;
            }
            // reset for the next one
            seeking = false;
         }
         if(actualDecodeStart != mCurrentPos)
            printf("ts not matching - now:%llu , last:%llu, lastlen:%llu, start %llu, len %llu\n",actualDecodeStart, mCurrentPos, mCurrentLen, start, len);
            //if we've skipped over some samples, fill the gap with silence.  This could happen often in the beginning of the file.
         if(actualDecodeStart>start && firstpass) {
            // find the number of samples for the leading silence
            int amt = actualDecodeStart - start;
            FFMpegDecodeCache* cache = new FFMpegDecodeCache;

            //printf("skipping/zeroing %i samples. - now:%llu (%f), last:%llu, lastlen:%llu, start %llu, len %llu\n",amt,actualDecodeStart, actualDecodeStartdouble, mCurrentPos, mCurrentLen, start, len);

//.........这里部分代码省略.........