Ejemplo n.º 1
0
static GstFlowReturn
opus_dec_chain_parse_data (GstOpusDec * dec, GstBuffer * buffer)
{
  GstFlowReturn res = GST_FLOW_OK;
  gsize size;
  guint8 *data;
  GstBuffer *outbuf;
  gint16 *out_data;
  int n, err;
  int samples;
  unsigned int packet_size;
  GstBuffer *buf;
  GstMapInfo map, omap;

  if (dec->state == NULL) {
    /* If we did not get any headers, default to 2 channels */
    if (dec->n_channels == 0) {
      GST_INFO_OBJECT (dec, "No header, assuming single stream");
      dec->n_channels = 2;
      dec->sample_rate = 48000;
      /* default stereo mapping */
      dec->channel_mapping_family = 0;
      dec->channel_mapping[0] = 0;
      dec->channel_mapping[1] = 1;
      dec->n_streams = 1;
      dec->n_stereo_streams = 1;

      gst_opus_dec_negotiate (dec, NULL);
    }

    GST_DEBUG_OBJECT (dec, "Creating decoder with %d channels, %d Hz",
        dec->n_channels, dec->sample_rate);
#ifndef GST_DISABLE_GST_DEBUG
    gst_opus_common_log_channel_mapping_table (GST_ELEMENT (dec), opusdec_debug,
        "Mapping table", dec->n_channels, dec->channel_mapping);
#endif

    GST_DEBUG_OBJECT (dec, "%d streams, %d stereo", dec->n_streams,
        dec->n_stereo_streams);
    dec->state =
        opus_multistream_decoder_create (dec->sample_rate, dec->n_channels,
        dec->n_streams, dec->n_stereo_streams, dec->channel_mapping, &err);
    if (!dec->state || err != OPUS_OK)
      goto creation_failed;
  }

  if (buffer) {
    GST_DEBUG_OBJECT (dec, "Received buffer of size %" G_GSIZE_FORMAT,
        gst_buffer_get_size (buffer));
  } else {
    GST_DEBUG_OBJECT (dec, "Received missing buffer");
  }

  /* if using in-band FEC, we introdude one extra frame's delay as we need
     to potentially wait for next buffer to decode a missing buffer */
  if (dec->use_inband_fec && !dec->primed) {
    GST_DEBUG_OBJECT (dec, "First buffer received in FEC mode, early out");
    gst_buffer_replace (&dec->last_buffer, buffer);
    dec->primed = TRUE;
    goto done;
  }

  /* That's the buffer we'll be sending to the opus decoder. */
  buf = (dec->use_inband_fec
      && gst_buffer_get_size (dec->last_buffer) >
      0) ? dec->last_buffer : buffer;

  if (buf && gst_buffer_get_size (buf) > 0) {
    gst_buffer_map (buf, &map, GST_MAP_READ);
    data = map.data;
    size = map.size;
    GST_DEBUG_OBJECT (dec, "Using buffer of size %" G_GSIZE_FORMAT, size);
  } else {
    /* concealment data, pass NULL as the bits parameters */
    GST_DEBUG_OBJECT (dec, "Using NULL buffer");
    data = NULL;
    size = 0;
  }

  /* use maximum size (120 ms) as the number of returned samples is
     not constant over the stream. */
  samples = 120 * dec->sample_rate / 1000;
  packet_size = samples * dec->n_channels * 2;

  outbuf =
      gst_audio_decoder_allocate_output_buffer (GST_AUDIO_DECODER (dec),
      packet_size);
  if (!outbuf) {
    goto buffer_failed;
  }

  gst_buffer_map (outbuf, &omap, GST_MAP_WRITE);
  out_data = (gint16 *) omap.data;

  if (dec->use_inband_fec) {
    if (dec->last_buffer) {
      /* normal delayed decode */
      GST_LOG_OBJECT (dec, "FEC enabled, decoding last delayed buffer");
      n = opus_multistream_decode (dec->state, data, size, out_data, samples,
          0);
    } else {
      /* FEC reconstruction decode */
      GST_LOG_OBJECT (dec, "FEC enabled, reconstructing last buffer");
      n = opus_multistream_decode (dec->state, data, size, out_data, samples,
          1);
    }
  } else {
    /* normal decode */
    GST_LOG_OBJECT (dec, "FEC disabled, decoding buffer");
    n = opus_multistream_decode (dec->state, data, size, out_data, samples, 0);
  }
  gst_buffer_unmap (outbuf, &omap);
  if (data != NULL)
    gst_buffer_unmap (buf, &map);

  if (n < 0) {
    GST_ELEMENT_ERROR (dec, STREAM, DECODE, ("Decoding error: %d", n), (NULL));
    gst_buffer_unref (outbuf);
    return GST_FLOW_ERROR;
  }
  GST_DEBUG_OBJECT (dec, "decoded %d samples", n);
  gst_buffer_set_size (outbuf, n * 2 * dec->n_channels);

  /* Skip any samples that need skipping */
  if (dec->pre_skip > 0) {
    guint scaled_pre_skip = dec->pre_skip * dec->sample_rate / 48000;
    guint skip = scaled_pre_skip > n ? n : scaled_pre_skip;
    guint scaled_skip = skip * 48000 / dec->sample_rate;

    gst_buffer_resize (outbuf, skip * 2 * dec->n_channels, -1);
    dec->pre_skip -= scaled_skip;
    GST_INFO_OBJECT (dec,
        "Skipping %u samples (%u at 48000 Hz, %u left to skip)", skip,
        scaled_skip, dec->pre_skip);
  }

  if (gst_buffer_get_size (outbuf) == 0) {
    gst_buffer_unref (outbuf);
    outbuf = NULL;
  } else if (dec->opus_pos[0] != GST_AUDIO_CHANNEL_POSITION_INVALID) {
    gst_audio_buffer_reorder_channels (outbuf, GST_AUDIO_FORMAT_S16,
        dec->n_channels, dec->opus_pos, dec->info.position);
  }

  /* Apply gain */
  /* Would be better off leaving this to a volume element, as this is
     a naive conversion that does too many int/float conversions.
     However, we don't have control over the pipeline...
     So make it optional if the user program wants to use a volume,
     but do it by default so the correct volume goes out by default */
  if (dec->apply_gain && outbuf && dec->r128_gain) {
    gsize rsize;
    unsigned int i, nsamples;
    double volume = dec->r128_gain_volume;
    gint16 *samples;

    gst_buffer_map (outbuf, &omap, GST_MAP_READWRITE);
    samples = (gint16 *) omap.data;
    rsize = omap.size;
    GST_DEBUG_OBJECT (dec, "Applying gain: volume %f", volume);
    nsamples = rsize / 2;
    for (i = 0; i < nsamples; ++i) {
      int sample = (int) (samples[i] * volume + 0.5);
      samples[i] = sample < -32768 ? -32768 : sample > 32767 ? 32767 : sample;
    }
    gst_buffer_unmap (outbuf, &omap);
  }

  if (dec->use_inband_fec) {
    gst_buffer_replace (&dec->last_buffer, buffer);
  }

  res = gst_audio_decoder_finish_frame (GST_AUDIO_DECODER (dec), outbuf, 1);

  if (res != GST_FLOW_OK)
    GST_DEBUG_OBJECT (dec, "flow: %s", gst_flow_get_name (res));

done:
  return res;

creation_failed:
  GST_ERROR_OBJECT (dec, "Failed to create Opus decoder: %d", err);
  return GST_FLOW_ERROR;

buffer_failed:
  GST_ERROR_OBJECT (dec, "Failed to create %u byte buffer", packet_size);
  return GST_FLOW_ERROR;
}
Ejemplo n.º 2
0
static gboolean
gst_opus_dec_set_format (GstAudioDecoder * bdec, GstCaps * caps)
{
  GstOpusDec *dec = GST_OPUS_DEC (bdec);
  gboolean ret = TRUE;
  GstStructure *s;
  const GValue *streamheader;
  GstCaps *old_caps;

  GST_DEBUG_OBJECT (dec, "set_format: %" GST_PTR_FORMAT, caps);

  if ((old_caps = gst_pad_get_current_caps (GST_AUDIO_DECODER_SINK_PAD (bdec)))) {
    if (gst_caps_is_equal (caps, old_caps)) {
      gst_caps_unref (old_caps);
      GST_DEBUG_OBJECT (dec, "caps didn't change");
      goto done;
    }

    GST_DEBUG_OBJECT (dec, "caps have changed, resetting decoder");
    gst_opus_dec_reset (dec);
    gst_caps_unref (old_caps);
  }

  s = gst_caps_get_structure (caps, 0);
  if ((streamheader = gst_structure_get_value (s, "streamheader")) &&
      G_VALUE_HOLDS (streamheader, GST_TYPE_ARRAY) &&
      gst_value_array_get_size (streamheader) >= 2) {
    const GValue *header, *vorbiscomment;
    GstBuffer *buf;
    GstFlowReturn res = GST_FLOW_OK;

    header = gst_value_array_get_value (streamheader, 0);
    if (header && G_VALUE_HOLDS (header, GST_TYPE_BUFFER)) {
      buf = gst_value_get_buffer (header);
      res = gst_opus_dec_parse_header (dec, buf);
      if (res != GST_FLOW_OK)
        goto done;
      gst_buffer_replace (&dec->streamheader, buf);
    }

    vorbiscomment = gst_value_array_get_value (streamheader, 1);
    if (vorbiscomment && G_VALUE_HOLDS (vorbiscomment, GST_TYPE_BUFFER)) {
      buf = gst_value_get_buffer (vorbiscomment);
      res = gst_opus_dec_parse_comments (dec, buf);
      if (res != GST_FLOW_OK)
        goto done;
      gst_buffer_replace (&dec->vorbiscomment, buf);
    }
  } else {
    /* defaults if not in the caps */
    dec->n_channels = 2;
    dec->sample_rate = 48000;

    gst_structure_get_int (s, "channels", &dec->n_channels);
    gst_structure_get_int (s, "rate", &dec->sample_rate);

    /* default stereo mapping */
    dec->channel_mapping_family = 0;
    dec->channel_mapping[0] = 0;
    dec->channel_mapping[1] = 1;
    dec->n_streams = 1;
    dec->n_stereo_streams = 1;

    gst_opus_dec_negotiate (dec, NULL);
  }

done:
  return ret;
}
Ejemplo n.º 3
0
static GstFlowReturn
gst_opus_dec_parse_header (GstOpusDec * dec, GstBuffer * buf)
{
  const guint8 *data;
  GstAudioChannelPosition pos[64];
  const GstAudioChannelPosition *posn = NULL;
  GstMapInfo map;

  if (!gst_opus_header_is_id_header (buf)) {
    GST_ERROR_OBJECT (dec, "Header is not an Opus ID header");
    return GST_FLOW_ERROR;
  }

  gst_buffer_map (buf, &map, GST_MAP_READ);
  data = map.data;

  if (!(dec->n_channels == 0 || dec->n_channels == data[9])) {
    gst_buffer_unmap (buf, &map);
    GST_ERROR_OBJECT (dec, "Opus ID header has invalid channels");
    return GST_FLOW_ERROR;
  }

  dec->n_channels = data[9];
  dec->sample_rate = GST_READ_UINT32_LE (data + 12);
  dec->pre_skip = GST_READ_UINT16_LE (data + 10);
  dec->r128_gain = GST_READ_UINT16_LE (data + 16);
  dec->r128_gain_volume = gst_opus_dec_get_r128_volume (dec->r128_gain);
  GST_INFO_OBJECT (dec,
      "Found pre-skip of %u samples, R128 gain %d (volume %f)",
      dec->pre_skip, dec->r128_gain, dec->r128_gain_volume);

  dec->channel_mapping_family = data[18];
  if (dec->channel_mapping_family == 0) {
    /* implicit mapping */
    GST_INFO_OBJECT (dec, "Channel mapping family 0, implicit mapping");
    dec->n_streams = dec->n_stereo_streams = 1;
    dec->channel_mapping[0] = 0;
    dec->channel_mapping[1] = 1;
  } else {
    dec->n_streams = data[19];
    dec->n_stereo_streams = data[20];
    memcpy (dec->channel_mapping, data + 21, dec->n_channels);

    if (dec->channel_mapping_family == 1) {
      GST_INFO_OBJECT (dec, "Channel mapping family 1, Vorbis mapping");
      switch (dec->n_channels) {
        case 1:
        case 2:
          /* nothing */
          break;
        case 3:
        case 4:
        case 5:
        case 6:
        case 7:
        case 8:
          posn = gst_opus_channel_positions[dec->n_channels - 1];
          break;
        default:{
          gint i;

          GST_ELEMENT_WARNING (GST_ELEMENT (dec), STREAM, DECODE,
              (NULL), ("Using NONE channel layout for more than 8 channels"));

          for (i = 0; i < dec->n_channels; i++)
            pos[i] = GST_AUDIO_CHANNEL_POSITION_NONE;

          posn = pos;
        }
      }
    } else {
      GST_INFO_OBJECT (dec, "Channel mapping family %d",
          dec->channel_mapping_family);
    }
  }

  gst_opus_dec_negotiate (dec, posn);

  gst_buffer_unmap (buf, &map);

  return GST_FLOW_OK;
}
static gboolean
gst_opus_dec_set_format (GstAudioDecoder * bdec, GstCaps * caps)
{
  GstOpusDec *dec = GST_OPUS_DEC (bdec);
  gboolean ret = TRUE;
  GstStructure *s;
  const GValue *streamheader;
  GstCaps *old_caps;

  GST_DEBUG_OBJECT (dec, "set_format: %" GST_PTR_FORMAT, caps);

  if ((old_caps = gst_pad_get_current_caps (GST_AUDIO_DECODER_SINK_PAD (bdec)))) {
    if (gst_caps_is_equal (caps, old_caps)) {
      gst_caps_unref (old_caps);
      GST_DEBUG_OBJECT (dec, "caps didn't change");
      goto done;
    }

    GST_DEBUG_OBJECT (dec, "caps have changed, resetting decoder");
    gst_opus_dec_reset (dec);
    gst_caps_unref (old_caps);
  }

  s = gst_caps_get_structure (caps, 0);
  if ((streamheader = gst_structure_get_value (s, "streamheader")) &&
      G_VALUE_HOLDS (streamheader, GST_TYPE_ARRAY) &&
      gst_value_array_get_size (streamheader) >= 2) {
    const GValue *header, *vorbiscomment;
    GstBuffer *buf;
    GstFlowReturn res = GST_FLOW_OK;

    header = gst_value_array_get_value (streamheader, 0);
    if (header && G_VALUE_HOLDS (header, GST_TYPE_BUFFER)) {
      buf = gst_value_get_buffer (header);
      res = gst_opus_dec_parse_header (dec, buf);
      if (res != GST_FLOW_OK) {
        ret = FALSE;
        goto done;
      }
      gst_buffer_replace (&dec->streamheader, buf);
    }

    vorbiscomment = gst_value_array_get_value (streamheader, 1);
    if (vorbiscomment && G_VALUE_HOLDS (vorbiscomment, GST_TYPE_BUFFER)) {
      buf = gst_value_get_buffer (vorbiscomment);
      res = gst_opus_dec_parse_comments (dec, buf);
      if (res != GST_FLOW_OK) {
        ret = FALSE;
        goto done;
      }
      gst_buffer_replace (&dec->vorbiscomment, buf);
    }
  } else {
    const GstAudioChannelPosition *posn = NULL;

    if (!gst_codec_utils_opus_parse_caps (caps, &dec->sample_rate,
            &dec->n_channels, &dec->channel_mapping_family, &dec->n_streams,
            &dec->n_stereo_streams, dec->channel_mapping)) {
      ret = FALSE;
      goto done;
    }

    if (dec->channel_mapping_family == 1 && dec->n_channels <= 8)
      posn = gst_opus_channel_positions[dec->n_channels - 1];

    if (!gst_opus_dec_negotiate (dec, posn))
      return FALSE;
  }

done:
  return ret;
}
static GstFlowReturn
opus_dec_chain_parse_data (GstOpusDec * dec, GstBuffer * buffer)
{
  GstFlowReturn res = GST_FLOW_OK;
  gsize size;
  guint8 *data;
  GstBuffer *outbuf, *bufd;
  gint16 *out_data;
  int n, err;
  int samples;
  unsigned int packet_size;
  GstBuffer *buf;
  GstMapInfo map, omap;
  GstAudioClippingMeta *cmeta = NULL;

  if (dec->state == NULL) {
    /* If we did not get any headers, default to 2 channels */
    if (dec->n_channels == 0) {
      GST_INFO_OBJECT (dec, "No header, assuming single stream");
      dec->n_channels = 2;
      dec->sample_rate = 48000;
      /* default stereo mapping */
      dec->channel_mapping_family = 0;
      dec->channel_mapping[0] = 0;
      dec->channel_mapping[1] = 1;
      dec->n_streams = 1;
      dec->n_stereo_streams = 1;

      if (!gst_opus_dec_negotiate (dec, NULL))
        return GST_FLOW_NOT_NEGOTIATED;
    }

    if (dec->n_channels == 2 && dec->n_streams == 1
        && dec->n_stereo_streams == 0) {
      /* if we are automatically decoding 2 channels, but only have
         a single encoded one, direct both channels to it */
      dec->channel_mapping[1] = 0;
    }

    GST_DEBUG_OBJECT (dec, "Creating decoder with %d channels, %d Hz",
        dec->n_channels, dec->sample_rate);
#ifndef GST_DISABLE_GST_DEBUG
    gst_opus_common_log_channel_mapping_table (GST_ELEMENT (dec), opusdec_debug,
        "Mapping table", dec->n_channels, dec->channel_mapping);
#endif

    GST_DEBUG_OBJECT (dec, "%d streams, %d stereo", dec->n_streams,
        dec->n_stereo_streams);
    dec->state =
        opus_multistream_decoder_create (dec->sample_rate, dec->n_channels,
        dec->n_streams, dec->n_stereo_streams, dec->channel_mapping, &err);
    if (!dec->state || err != OPUS_OK)
      goto creation_failed;
  }

  if (buffer) {
    GST_DEBUG_OBJECT (dec, "Received buffer of size %" G_GSIZE_FORMAT,
        gst_buffer_get_size (buffer));
  } else {
    GST_DEBUG_OBJECT (dec, "Received missing buffer");
  }

  /* if using in-band FEC, we introdude one extra frame's delay as we need
     to potentially wait for next buffer to decode a missing buffer */
  if (dec->use_inband_fec && !dec->primed) {
    GST_DEBUG_OBJECT (dec, "First buffer received in FEC mode, early out");
    gst_buffer_replace (&dec->last_buffer, buffer);
    dec->primed = TRUE;
    goto done;
  }

  /* That's the buffer we'll be sending to the opus decoder. */
  buf = (dec->use_inband_fec
      && gst_buffer_get_size (dec->last_buffer) >
      0) ? dec->last_buffer : buffer;

  /* That's the buffer we get duration from */
  bufd = dec->use_inband_fec ? dec->last_buffer : buffer;

  if (buf && gst_buffer_get_size (buf) > 0) {
    gst_buffer_map (buf, &map, GST_MAP_READ);
    data = map.data;
    size = map.size;
    GST_DEBUG_OBJECT (dec, "Using buffer of size %" G_GSIZE_FORMAT, size);
  } else {
    /* concealment data, pass NULL as the bits parameters */
    GST_DEBUG_OBJECT (dec, "Using NULL buffer");
    data = NULL;
    size = 0;
  }

  if (gst_buffer_get_size (bufd) == 0) {
    GstClockTime const opus_plc_alignment = 2500 * GST_USECOND;
    GstClockTime aligned_missing_duration;
    GstClockTime missing_duration = GST_BUFFER_DURATION (bufd);

    if (!GST_CLOCK_TIME_IS_VALID (missing_duration) || missing_duration == 0) {
      if (GST_CLOCK_TIME_IS_VALID (dec->last_known_buffer_duration)) {
        missing_duration = dec->last_known_buffer_duration;
        GST_WARNING_OBJECT (dec,
            "Missing duration, using last duration %" GST_TIME_FORMAT,
            GST_TIME_ARGS (missing_duration));
      } else {
        GST_WARNING_OBJECT (dec,
            "Missing buffer, but unknown duration, and no previously known duration, assuming 20 ms");
        missing_duration = 20 * GST_MSECOND;
      }
    }

    GST_DEBUG_OBJECT (dec,
        "missing buffer, doing PLC duration %" GST_TIME_FORMAT
        " plus leftover %" GST_TIME_FORMAT, GST_TIME_ARGS (missing_duration),
        GST_TIME_ARGS (dec->leftover_plc_duration));

    /* add the leftover PLC duration to that of the buffer */
    missing_duration += dec->leftover_plc_duration;

    /* align the combined buffer and leftover PLC duration to multiples
     * of 2.5ms, rounding to nearest, and store excess duration for later */
    aligned_missing_duration =
        ((missing_duration +
            opus_plc_alignment / 2) / opus_plc_alignment) * opus_plc_alignment;
    dec->leftover_plc_duration = missing_duration - aligned_missing_duration;

    /* Opus' PLC cannot operate with less than 2.5ms; skip PLC
     * and accumulate the missing duration in the leftover_plc_duration
     * for the next PLC attempt */
    if (aligned_missing_duration < opus_plc_alignment) {
      GST_DEBUG_OBJECT (dec,
          "current duration %" GST_TIME_FORMAT
          " of missing data not enough for PLC (minimum needed: %"
          GST_TIME_FORMAT ") - skipping", GST_TIME_ARGS (missing_duration),
          GST_TIME_ARGS (opus_plc_alignment));
      goto done;
    }

    /* convert the duration (in nanoseconds) to sample count */
    samples =
        gst_util_uint64_scale_int (aligned_missing_duration, dec->sample_rate,
        GST_SECOND);

    GST_DEBUG_OBJECT (dec,
        "calculated PLC frame length: %" GST_TIME_FORMAT
        " num frame samples: %d new leftover: %" GST_TIME_FORMAT,
        GST_TIME_ARGS (aligned_missing_duration), samples,
        GST_TIME_ARGS (dec->leftover_plc_duration));
  } else {
    /* use maximum size (120 ms) as the number of returned samples is
       not constant over the stream. */
    samples = 120 * dec->sample_rate / 1000;
  }
  packet_size = samples * dec->n_channels * 2;

  outbuf =
      gst_audio_decoder_allocate_output_buffer (GST_AUDIO_DECODER (dec),
      packet_size);
  if (!outbuf) {
    goto buffer_failed;
  }

  if (size > 0)
    dec->last_known_buffer_duration = packet_duration_opus (data, size);

  gst_buffer_map (outbuf, &omap, GST_MAP_WRITE);
  out_data = (gint16 *) omap.data;

  do {
    if (dec->use_inband_fec) {
      if (gst_buffer_get_size (dec->last_buffer) > 0) {
        /* normal delayed decode */
        GST_LOG_OBJECT (dec, "FEC enabled, decoding last delayed buffer");
        n = opus_multistream_decode (dec->state, data, size, out_data, samples,
            0);
      } else {
        /* FEC reconstruction decode */
        GST_LOG_OBJECT (dec, "FEC enabled, reconstructing last buffer");
        n = opus_multistream_decode (dec->state, data, size, out_data, samples,
            1);
      }
    } else {
      /* normal decode */
      GST_LOG_OBJECT (dec, "FEC disabled, decoding buffer");
      n = opus_multistream_decode (dec->state, data, size, out_data, samples,
          0);
    }
    if (n == OPUS_BUFFER_TOO_SMALL) {
      /* if too small, add 2.5 milliseconds and try again, up to the
       * Opus max size of 120 milliseconds */
      if (samples >= 120 * dec->sample_rate / 1000)
        break;
      samples += 25 * dec->sample_rate / 10000;
      packet_size = samples * dec->n_channels * 2;
      gst_buffer_unmap (outbuf, &omap);
      gst_buffer_unref (outbuf);
      outbuf =
          gst_audio_decoder_allocate_output_buffer (GST_AUDIO_DECODER (dec),
          packet_size);
      if (!outbuf) {
        goto buffer_failed;
      }
      gst_buffer_map (outbuf, &omap, GST_MAP_WRITE);
      out_data = (gint16 *) omap.data;
    }
  } while (n == OPUS_BUFFER_TOO_SMALL);
  gst_buffer_unmap (outbuf, &omap);
  if (data != NULL)
    gst_buffer_unmap (buf, &map);

  if (n < 0) {
    GstFlowReturn ret = GST_FLOW_ERROR;

    gst_buffer_unref (outbuf);
    GST_AUDIO_DECODER_ERROR (dec, 1, STREAM, DECODE, (NULL),
        ("Decoding error (%d): %s", n, opus_strerror (n)), ret);
    return ret;
  }
  GST_DEBUG_OBJECT (dec, "decoded %d samples", n);
  gst_buffer_set_size (outbuf, n * 2 * dec->n_channels);
  GST_BUFFER_DURATION (outbuf) = samples * GST_SECOND / dec->sample_rate;
  samples = n;

  cmeta = gst_buffer_get_audio_clipping_meta (buf);

  g_assert (!cmeta || cmeta->format == GST_FORMAT_DEFAULT);

  /* Skip any samples that need skipping */
  if (cmeta && cmeta->start) {
    guint pre_skip = cmeta->start;
    guint scaled_pre_skip = pre_skip * dec->sample_rate / 48000;
    guint skip = scaled_pre_skip > n ? n : scaled_pre_skip;
    guint scaled_skip = skip * 48000 / dec->sample_rate;

    gst_buffer_resize (outbuf, skip * 2 * dec->n_channels, -1);

    GST_INFO_OBJECT (dec,
        "Skipping %u samples at the beginning (%u at 48000 Hz)",
        skip, scaled_skip);
  }

  if (cmeta && cmeta->end) {
    guint post_skip = cmeta->end;
    guint scaled_post_skip = post_skip * dec->sample_rate / 48000;
    guint skip = scaled_post_skip > n ? n : scaled_post_skip;
    guint scaled_skip = skip * 48000 / dec->sample_rate;
    guint outsize = gst_buffer_get_size (outbuf);
    guint skip_bytes = skip * 2 * dec->n_channels;

    if (outsize > skip_bytes)
      outsize -= skip_bytes;
    else
      outsize = 0;

    gst_buffer_resize (outbuf, 0, outsize);

    GST_INFO_OBJECT (dec,
        "Skipping %u samples at the end (%u at 48000 Hz)", skip, scaled_skip);
  }

  if (gst_buffer_get_size (outbuf) == 0) {
    gst_buffer_unref (outbuf);
    outbuf = NULL;
  } else if (dec->opus_pos[0] != GST_AUDIO_CHANNEL_POSITION_INVALID) {
    gst_audio_buffer_reorder_channels (outbuf, GST_AUDIO_FORMAT_S16,
        dec->n_channels, dec->opus_pos, dec->info.position);
  }

  /* Apply gain */
  /* Would be better off leaving this to a volume element, as this is
     a naive conversion that does too many int/float conversions.
     However, we don't have control over the pipeline...
     So make it optional if the user program wants to use a volume,
     but do it by default so the correct volume goes out by default */
  if (dec->apply_gain && outbuf && dec->r128_gain) {
    gsize rsize;
    unsigned int i, nsamples;
    double volume = dec->r128_gain_volume;
    gint16 *samples;

    gst_buffer_map (outbuf, &omap, GST_MAP_READWRITE);
    samples = (gint16 *) omap.data;
    rsize = omap.size;
    GST_DEBUG_OBJECT (dec, "Applying gain: volume %f", volume);
    nsamples = rsize / 2;
    for (i = 0; i < nsamples; ++i) {
      int sample = (int) (samples[i] * volume + 0.5);
      samples[i] = sample < -32768 ? -32768 : sample > 32767 ? 32767 : sample;
    }
    gst_buffer_unmap (outbuf, &omap);
  }

  if (dec->use_inband_fec) {
    gst_buffer_replace (&dec->last_buffer, buffer);
  }

  res = gst_audio_decoder_finish_frame (GST_AUDIO_DECODER (dec), outbuf, 1);

  if (res != GST_FLOW_OK)
    GST_DEBUG_OBJECT (dec, "flow: %s", gst_flow_get_name (res));

done:
  return res;

creation_failed:
  GST_ELEMENT_ERROR (dec, LIBRARY, INIT, ("Failed to create Opus decoder"),
      ("Failed to create Opus decoder (%d): %s", err, opus_strerror (err)));
  return GST_FLOW_ERROR;

buffer_failed:
  GST_ELEMENT_ERROR (dec, STREAM, DECODE, (NULL),
      ("Failed to create %u byte buffer", packet_size));
  return GST_FLOW_ERROR;
}
static GstFlowReturn
gst_opus_dec_parse_header (GstOpusDec * dec, GstBuffer * buf)
{
  GstAudioChannelPosition pos[64];
  const GstAudioChannelPosition *posn = NULL;

  if (!gst_opus_header_is_id_header (buf)) {
    GST_ELEMENT_ERROR (dec, STREAM, FORMAT, (NULL),
        ("Header is not an Opus ID header"));
    return GST_FLOW_ERROR;
  }

  if (!gst_codec_utils_opus_parse_header (buf,
          &dec->sample_rate,
          &dec->n_channels,
          &dec->channel_mapping_family,
          &dec->n_streams,
          &dec->n_stereo_streams,
          dec->channel_mapping, &dec->pre_skip, &dec->r128_gain)) {
    GST_ELEMENT_ERROR (dec, STREAM, DECODE, (NULL),
        ("Failed to parse Opus ID header"));
    return GST_FLOW_ERROR;
  }
  dec->r128_gain_volume = gst_opus_dec_get_r128_volume (dec->r128_gain);

  GST_INFO_OBJECT (dec,
      "Found pre-skip of %u samples, R128 gain %d (volume %f)",
      dec->pre_skip, dec->r128_gain, dec->r128_gain_volume);

  if (dec->channel_mapping_family == 1) {
    GST_INFO_OBJECT (dec, "Channel mapping family 1, Vorbis mapping");
    switch (dec->n_channels) {
      case 1:
      case 2:
        /* nothing */
        break;
      case 3:
      case 4:
      case 5:
      case 6:
      case 7:
      case 8:
        posn = gst_opus_channel_positions[dec->n_channels - 1];
        break;
      default:{
        gint i;

        GST_ELEMENT_WARNING (GST_ELEMENT (dec), STREAM, DECODE,
            (NULL), ("Using NONE channel layout for more than 8 channels"));

        for (i = 0; i < dec->n_channels; i++)
          pos[i] = GST_AUDIO_CHANNEL_POSITION_NONE;

        posn = pos;
      }
    }
  } else {
    GST_INFO_OBJECT (dec, "Channel mapping family %d",
        dec->channel_mapping_family);
  }

  if (!gst_opus_dec_negotiate (dec, posn))
    return GST_FLOW_NOT_NEGOTIATED;

  return GST_FLOW_OK;
}
static GstFlowReturn
gst_opus_dec_parse_header (GstOpusDec * dec, GstBuffer * buf)
{
  const guint8 *data = GST_BUFFER_DATA (buf);
  GstCaps *caps;
  const GstAudioChannelPosition *pos = NULL;

  if (!gst_opus_header_is_id_header (buf)) {
    GST_ERROR_OBJECT (dec, "Header is not an Opus ID header");
    return GST_FLOW_ERROR;
  }
  if (!(dec->n_channels == 0 || dec->n_channels == data[9])) {
    GST_ERROR_OBJECT (dec, "Opus ID header has invalid channels");
    return GST_FLOW_ERROR;
  }

  dec->n_channels = data[9];
  dec->pre_skip = GST_READ_UINT16_LE (data + 10);
  dec->r128_gain = GST_READ_UINT16_LE (data + 16);
  dec->r128_gain_volume = gst_opus_dec_get_r128_volume (dec->r128_gain);
  GST_INFO_OBJECT (dec,
      "Found pre-skip of %u samples, R128 gain %d (volume %f)",
      dec->pre_skip, dec->r128_gain, dec->r128_gain_volume);

  dec->channel_mapping_family = data[18];
  if (dec->channel_mapping_family == 0) {
    /* implicit mapping */
    GST_INFO_OBJECT (dec, "Channel mapping family 0, implicit mapping");
    dec->n_streams = dec->n_stereo_streams = 1;
    dec->channel_mapping[0] = 0;
    dec->channel_mapping[1] = 1;
  } else {
    dec->n_streams = data[19];
    dec->n_stereo_streams = data[20];
    memcpy (dec->channel_mapping, data + 21, dec->n_channels);

    if (dec->channel_mapping_family == 1) {
      GST_INFO_OBJECT (dec, "Channel mapping family 1, Vorbis mapping");
      switch (dec->n_channels) {
        case 1:
        case 2:
          /* nothing */
          break;
        case 3:
        case 4:
        case 5:
        case 6:
        case 7:
        case 8:
          pos = gst_opus_channel_positions[dec->n_channels - 1];
          break;
        default:{
          gint i;
          GstAudioChannelPosition *posn =
              g_new (GstAudioChannelPosition, dec->n_channels);

          GST_ELEMENT_WARNING (GST_ELEMENT (dec), STREAM, DECODE,
              (NULL), ("Using NONE channel layout for more than 8 channels"));

          for (i = 0; i < dec->n_channels; i++)
            posn[i] = GST_AUDIO_CHANNEL_POSITION_NONE;

          pos = posn;
        }
      }
    } else {
      GST_INFO_OBJECT (dec, "Channel mapping family %d",
          dec->channel_mapping_family);
    }
  }

  caps = gst_opus_dec_negotiate (dec);

  if (pos) {
    GST_DEBUG_OBJECT (dec, "Setting channel positions on caps");
    gst_audio_set_channel_positions (gst_caps_get_structure (caps, 0), pos);
  }

  if (dec->n_channels > 8) {
    g_free ((GstAudioChannelPosition *) pos);
  }

  GST_INFO_OBJECT (dec, "Setting src caps to %" GST_PTR_FORMAT, caps);
  gst_pad_set_caps (GST_AUDIO_DECODER_SRC_PAD (dec), caps);
  gst_caps_unref (caps);

  return GST_FLOW_OK;
}