[mythtv-commits] Ticket #10736: Fix passthrough case of mythtrancode running in fifo mode

[MythTV]

#10736: Fix passthrough case of mythtrancode running in fifo mode
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 Reporter:  mythtv@…                |          Owner:
     Type:  Patch - Bug Fix         |         Status:  new
 Priority:  minor                   |      Milestone:  unknown
Component:  MythTV - Mythtranscode  |        Version:  0.25-fixes
 Severity:  medium                  |     Resolution:
 Keywords:                          |  Ticket locked:  0
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Comment (by mythtv@…):

 JYA noticed another problem, to do with the accuracy of the timecode
 calculation. I've added a commit also to fix that, plus I've commented the
 algorith. Here's an updated pull request containing both commits:
 https://github.com/MythTV/mythtv/pull/21. To help anyone wishing to check
 this without applying the commits, here's the updated version of addData,
 which is the main change:

 {{{
     virtual bool AddData(void *buffer, int len, int64_t timecode, int
 frames)
     {
         unsigned char *buf = (unsigned char *)buffer;

         // Test if target is using a fixed buffer size.
         if (m_audioFrameSize)
         {
             int index = 0;
             int total_frames = 0;

             // Target has a fixed buffer size, which may not match len.
             // Redistribute the bytes into appropriately sized buffers.
             while (index < len)
             {
                 // See if we have some saved from last iteration in
                 // m_saveBuffer. If not create a new empty buffer.
                 if (!m_saveBuffer)
                     m_saveBuffer = new AudioBuffer();

                 // Use as many of the remaining frames as will fit in the
 space
                 // left in the buffer.
                 int part = min(len - index,
                                m_audioFrameSize -
 m_saveBuffer->m_buffer.size());
                 total_frames += part / m_bytes_per_frame;
                 timecode = total_frames * 1000 / m_eff_audiorate;
                 // Store frames in buffer, basing frame count on number of
 bytes,
                 // which works only for uncompressed data.
                 m_saveBuffer->appendData(&buf[index], part, part /
 m_bytes_per_frame,
                                          timecode);

                 // If we have filled the buffer...
                 if (m_saveBuffer->m_buffer.size() == m_audioFrameSize)
                 {
                     // store the buffer
                     m_bufferList.append(m_saveBuffer);
                     // mark m_saveBuffer as emtpy.
                     m_saveBuffer = NULL;
                     // m_last_audiotime is updated iff we store a buffer.
                     m_last_audiotime = timecode;
                 }

                 index += part;
             }
         }
         else
         {
             // Target has no fixed buffer size. We can use a simpler
 algorithm
             // and use 'frames' directly rather than 'len /
 m_bytes_per_frame',
             // thus also covering the passthrough case.
             m_saveBuffer = new AudioBuffer();
             timecode += frames * 1000 / m_eff_audiorate;
             m_saveBuffer->appendData(buf, len, frames, timecode);

             m_bufferList.append(m_saveBuffer);
             m_saveBuffer = NULL;
             m_last_audiotime = timecode;
         }

         return true;
     }
 }}}

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Ticket URL: <http://code.mythtv.org/trac/ticket/10736#comment:1>
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