C++ snd_pcm_frames_to_bytes函数代码示例

static int
write_alsa_output (char * output_data, int output_size) {
    int err;
    snd_pcm_uframes_t frames;

    while (output_size > 0) {
        frames = snd_pcm_bytes_to_frames(pcm, output_size);
        if ((err = snd_pcm_writei(pcm, output_data, frames)) < 0) {
            if (snd_pcm_state(pcm) == SND_PCM_STATE_XRUN) {
                if ((err = snd_pcm_prepare(pcm)) < 0)
                    printf("snd_pcm_prepare() failed.\r\n");
                alsa_first_time = 1;
                continue;
            }
            return err;
        }

        output_size -= snd_pcm_frames_to_bytes(pcm, err);
        output_data += snd_pcm_frames_to_bytes(pcm, err);
        if (alsa_first_time) {
            alsa_first_time = 0;
            snd_pcm_start(pcm);
        }
    }
    return 0;
}

static int snd_pcm_file_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t * params)
{
	snd_pcm_file_t *file = pcm->private_data;
	unsigned int channel;
	snd_pcm_t *slave = file->gen.slave;
	int err = _snd_pcm_hw_params(slave, params);
	if (err < 0)
		return err;
	file->buffer_bytes = snd_pcm_frames_to_bytes(slave, slave->buffer_size);
	file->wbuf_size = slave->buffer_size * 2;
	file->wbuf_size_bytes = snd_pcm_frames_to_bytes(slave, file->wbuf_size);
	file->wbuf_used_bytes = 0;
	assert(!file->wbuf);
	file->wbuf = malloc(file->wbuf_size_bytes);
	if (file->wbuf == NULL) {
		snd_pcm_file_hw_free(pcm);
		return -ENOMEM;
	}
	file->wbuf_areas = malloc(sizeof(*file->wbuf_areas) * slave->channels);
	if (file->wbuf_areas == NULL) {
		snd_pcm_file_hw_free(pcm);
		return -ENOMEM;
	}
	file->appl_ptr = file->file_ptr_bytes = 0;
	for (channel = 0; channel < slave->channels; ++channel) {
		snd_pcm_channel_area_t *a = &file->wbuf_areas[channel];
		a->addr = file->wbuf;
		a->first = slave->sample_bits * channel;
		a->step = slave->frame_bits;
	}
	return 0;
}

static ALuint ALSANoMMapProc(ALvoid *ptr)
{
    ALCdevice *Device = (ALCdevice*)ptr;
    alsa_data *data = (alsa_data*)Device->ExtraData;
    snd_pcm_sframes_t avail;
    char *WritePtr;

    SetRTPriority();

    while(!data->killNow)
    {
        int state = verify_state(data->pcmHandle);
        if(state < 0)
        {
            ERR("Invalid state detected: %s\n", snd_strerror(state));
            aluHandleDisconnect(Device);
            break;
        }

        WritePtr = data->buffer;
        avail = data->size / snd_pcm_frames_to_bytes(data->pcmHandle, 1);
        aluMixData(Device, WritePtr, avail);

        while(avail > 0)
        {
            int ret = snd_pcm_writei(data->pcmHandle, WritePtr, avail);
            switch (ret)
            {
            case -EAGAIN:
                continue;
            case -ESTRPIPE:
            case -EPIPE:
            case -EINTR:
                ret = snd_pcm_recover(data->pcmHandle, ret, 1);
                if(ret < 0)
                    avail = 0;
                break;
            default:
                if (ret >= 0)
                {
                    WritePtr += snd_pcm_frames_to_bytes(data->pcmHandle, ret);
                    avail -= ret;
                }
                break;
            }
            if (ret < 0)
            {
                ret = snd_pcm_prepare(data->pcmHandle);
                if(ret < 0)
                    break;
            }
        }
    }

    return 0;
}

int AudioInputALSA::PcmRead(void* buf, uint nbytes)
{
    unsigned char* bufptr = (unsigned char*)buf;
    snd_pcm_uframes_t to_read = snd_pcm_bytes_to_frames(pcm_handle, nbytes);
    snd_pcm_uframes_t nframes = to_read;
    snd_pcm_sframes_t nread, avail;
    int retries = 0;
    while (nframes > 0 && retries < 3)
    {
        if (AlsaBad((avail = snd_pcm_avail_update(pcm_handle)),
                    "available update failed"))
        {
            if (!Recovery(avail))
            {
                ++retries;
                continue;
            }
        }
        if ((nread = snd_pcm_readi(pcm_handle, bufptr, nframes)) < 0)
        {
            switch (nread)
            {
            case -EAGAIN:
                break;
            case -EBADFD:
                LOG(VB_GENERAL, LOG_ERR, LOC_DEV +
                    QString("in a state unfit to read (%1): %2")
                    .arg(nread).arg(snd_strerror(nread)));
                break;
            case -EINTR:
            case -EPIPE:
            case -ESTRPIPE:
                Recovery(nread);
                break;
            default:
                LOG(VB_GENERAL, LOG_ERR, LOC_DEV +
                    QString("weird return from snd_pcm_readi: %1")
                    .arg(snd_strerror(nread)));
                break;
            }
        }
        else
        {
            nframes -= nread;
            bufptr += snd_pcm_frames_to_bytes(pcm_handle, nread);
        }
        ++retries;
    }
    if (nframes > 0)
        LOG(VB_AUDIO, LOG_ERR, LOC_DEV +
            QString("short pcm read, %1 of %2 frames, retries %3")
            .arg(to_read - nframes).arg(to_read).arg(retries));
    return snd_pcm_frames_to_bytes(pcm_handle, to_read - nframes);
}

bool QAudioOutputPrivate::deviceReady()
{
    if(pullMode) {
        int l = 0;
        int chunks = bytesAvailable/period_size;
        if(chunks==0) {
            bytesAvailable = bytesFree();
            return false;
        }
#ifdef DEBUG_AUDIO
        qDebug()<<"deviceReady() avail="<<bytesAvailable<<" bytes, period size="<<period_size<<" bytes";
        qDebug()<<"deviceReady() no. of chunks that can fit ="<<chunks<<", chunks in bytes ="<<period_size*chunks;
#endif
        int input = period_frames*chunks;
        if(input > (int)buffer_frames)
            input = buffer_frames;
        l = audioSource->read(audioBuffer,snd_pcm_frames_to_bytes(handle, input));
        if(l > 0) {
            // Got some data to output
            if(deviceState != QAudio::ActiveState)
                return true;
            write(audioBuffer,l);
            bytesAvailable = bytesFree();

        } else if(l == 0) {
            // Did not get any data to output
            bytesAvailable = bytesFree();
            if(bytesAvailable > snd_pcm_frames_to_bytes(handle, buffer_frames-period_frames)) {
                // Underrun
                errorState = QAudio::UnderrunError;
                deviceState = QAudio::IdleState;
                emit stateChanged(deviceState);
            }

        } else if(l < 0) {
            close();
            errorState = QAudio::IOError;
            emit stateChanged(deviceState);
        }
    } else
        bytesAvailable = bytesFree();

    if(deviceState != QAudio::ActiveState)
        return true;

    if((timeStamp.elapsed() + elapsedTimeOffset) > intervalTime) {
        emit notify();
        elapsedTimeOffset = timeStamp.elapsed() + elapsedTimeOffset - intervalTime;
        timeStamp.restart();
    }
    return true;
}

static void alsa_stop_capture(ALCdevice *Device)
{
    alsa_data *data = (alsa_data*)Device->ExtraData;
    ALCuint avail;
    int err;

    /* OpenAL requires access to unread audio after stopping, but ALSA's
     * snd_pcm_drain is unreliable and snd_pcm_drop drops it. Capture what's
     * available now so it'll be available later after the drop. */
    avail = alsa_available_samples(Device);
    if(!data->ring && avail > 0)
    {
        /* The ring buffer implicitly captures when checking availability.
         * Direct access needs to explicitly capture it into temp storage. */
        ALsizei size;
        void *ptr;

        size = snd_pcm_frames_to_bytes(data->pcmHandle, avail);
        ptr = realloc(data->buffer, size);
        if(ptr)
        {
            data->buffer = ptr;
            alsa_capture_samples(Device, data->buffer, avail);
            data->size = size;
        }
    }
    err = snd_pcm_drop(data->pcmHandle);
    if(err < 0)
        ERR("drop failed: %s\n", snd_strerror(err));
    data->doCapture = AL_FALSE;
}

/**************************************************************************
 * 				wodUpdatePlayedTotal	[internal]
 *
 */
static BOOL wodUpdatePlayedTotal(WINE_WAVEDEV* wwo, snd_pcm_status_t* ps)
{
    snd_pcm_sframes_t delay;
    snd_pcm_sframes_t avail;
    snd_pcm_uframes_t buf_size = 0;
    snd_pcm_state_t state;

    state = snd_pcm_state(wwo->pcm);
    avail = snd_pcm_avail_update(wwo->pcm);
    snd_pcm_hw_params_get_buffer_size(wwo->hw_params, &buf_size);
    delay = buf_size - avail;

    if (state != SND_PCM_STATE_RUNNING && state != SND_PCM_STATE_PREPARED)
    {
        WARN("Unexpected state (%d) while updating Total Played, resetting\n", state);
        wine_snd_pcm_recover(wwo->pcm, -EPIPE, 0);
        delay=0;
    }

    /* A delay < 0 indicates an underrun; for our purposes that's 0.  */
    if (delay < 0)
    {
        WARN("Unexpected delay (%ld) while updating Total Played, resetting\n", delay);
        delay=0;
    }

    InterlockedExchange((LONG*)&wwo->dwPlayedTotal, wwo->dwWrittenTotal - snd_pcm_frames_to_bytes(wwo->pcm, delay));
    return TRUE;
}

int QAudioOutputPrivate::bytesFree() const
{
    if(resuming)
        return period_size;

    if(deviceState != QAudio::ActiveState && deviceState != QAudio::IdleState)
        return 0;

    int frames = snd_pcm_avail_update(handle);
    if (frames == -EPIPE) {
        // Try and handle buffer underrun
        int err = snd_pcm_recover(handle, frames, 0);
        if (err < 0)
            return 0;
        else
            frames = snd_pcm_avail_update(handle);
    } else if (frames < 0) {
        return 0;
    }

    if ((int)frames > (int)buffer_frames)
        frames = buffer_frames;

    return snd_pcm_frames_to_bytes(handle, frames);
}

EmErrorCode AlsaRenderer::Write(const char* buf, uint32_t len)
{
    int off = 0;
    int leftFrames = (len + m_FrameLength - 1) / m_FrameLength;

    while (leftFrames > 0) {
        int written = snd_pcm_writei(m_PcmHandle, buf+off, leftFrames);
        if (written > 0) {
            leftFrames -= written;
            off += snd_pcm_frames_to_bytes(m_PcmHandle, written);
        } else if (written == -EPIPE) {
            if (snd_pcm_prepare(m_PcmHandle) < 0)
                printf("FATAL: snd_pcm_prepare() failed!\n");
        } else if (written == -ESTRPIPE) {
            while ((written = snd_pcm_resume(m_PcmHandle)) == -EAGAIN)
                usleep(100);
            if (written < 0) {
                if ((written = snd_pcm_prepare(m_PcmHandle)) < 0)
                    return ErrorCode::RendererFailedToWrite;
            }
        } else if (written <= 0) {
            printf("writei error / short write\n");
        }
    }

    return ErrorCode::Ok;
}

qint64 QAudioInputPrivate::read( char *data, qint64 maxlen )
{
    int     rc = -1, count=0;

    if (handle != NULL)
    {
        while(count < 5) {
            int frames = snd_pcm_bytes_to_frames(handle, (int)maxlen);
            int readFrames = snd_pcm_readi(handle, data, frames);

            if (readFrames >= 0) {
                rc = snd_pcm_frames_to_bytes(handle, readFrames);
                qLog(QAudioInput) << QString("read in bytes = %1 (frames=%2)").arg(rc).arg(readFrames).toLatin1().constData();
                break;
            }
            else if ((readFrames == -EAGAIN) || (readFrames == -EINTR)) {
                qLog(QAudioInput) << "ALSA: EAGAIN || EINTR error";
                rc = 0;
                break;
            }
            else {
                if(readFrames == -EPIPE) {
                    qLog(QAudioInput) << "ALSA: underrun!!!";
                    rc = snd_pcm_prepare(handle);
                } else if(readFrames == -ESTRPIPE) {
                    qLog(QAudioInput) << "ALSA: suspend recovery!!!!";
                    rc = snd_pcm_prepare(handle);
                }
                if(rc != 0) break;
            }
            count++;
        }
    }
    return rc;
}

/* transfer data to audio h/w via normal write */
static void
alsa_write_audio(char* data, int length) {
	snd_pcm_sframes_t written_frames;

	while(length > 0) {
		int frames = snd_pcm_bytes_to_frames(alsa_pcm, length);
		written_frames = snd_pcm_writei(alsa_pcm, data, frames);

		if(written_frames > 0) {
			int written = snd_pcm_frames_to_bytes(alsa_pcm,
			                                      written_frames);
			length -= written;
			data += written;
			alsa_hw_written += written;
		} else {
			int err = alsa_handle_error((int) written_frames);

			if(err < 0) {
				printf("alsa_write_audio(): write error: %s\n",
				       snd_strerror(-err));
				break;
			}
		}
	}
}

void QAudioOutputPrivate::resume()
{
    if(deviceState == QAudio::SuspendedState) {
        int err = 0;

        if(handle) {
            err = snd_pcm_prepare( handle );
            if(err < 0)
                xrun_recovery(err);

            err = snd_pcm_start(handle);
            if(err < 0)
                xrun_recovery(err);

            bytesAvailable = (int)snd_pcm_frames_to_bytes(handle, buffer_frames);
        }
        resuming = true;
        if(pullMode)
            deviceState = QAudio::ActiveState;
        else
            deviceState = QAudio::IdleState;

        errorState = QAudio::NoError;
        timer->start(period_time/1000);
        emit stateChanged(deviceState);
    }
}

static guint
gst_alsasink_write (GstAudioSink * asink, gpointer data, guint length)
{
    GstAlsaSink *alsa;
    gint err;
    gint cptr;
    gint16 *ptr = data;

    alsa = GST_ALSA_SINK (asink);

    if (alsa->iec958 && alsa->need_swap) {
        guint i;

        GST_DEBUG_OBJECT (asink, "swapping bytes");
        for (i = 0; i < length / 2; i++) {
            ptr[i] = GUINT16_SWAP_LE_BE (ptr[i]);
        }
    }

    GST_LOG_OBJECT (asink, "received audio samples buffer of %u bytes", length);

    cptr = length / alsa->bytes_per_sample;

    GST_ALSA_SINK_LOCK (asink);
    while (cptr > 0) {
        /* start by doing a blocking wait for free space. Set the timeout
         * to 4 times the period time */
        err = snd_pcm_wait (alsa->handle, (4 * alsa->period_time / 1000));
        if (err < 0) {
            GST_DEBUG_OBJECT (asink, "wait error, %d", err);
        } else {
            GST_DELAY_SINK_LOCK (asink);
            err = snd_pcm_writei (alsa->handle, ptr, cptr);
            GST_DELAY_SINK_UNLOCK (asink);
        }

        GST_DEBUG_OBJECT (asink, "written %d frames out of %d", err, cptr);
        if (err < 0) {
            GST_DEBUG_OBJECT (asink, "Write error: %s", snd_strerror (err));
            if (err == -EAGAIN) {
                continue;
            } else if (xrun_recovery (alsa, alsa->handle, err) < 0) {
                goto write_error;
            }
            continue;
        }

        ptr += snd_pcm_frames_to_bytes (alsa->handle, err);
        cptr -= err;
    }
    GST_ALSA_SINK_UNLOCK (asink);

    return length - (cptr * alsa->bytes_per_sample);

write_error:
    {
        GST_ALSA_SINK_UNLOCK (asink);
        return length;              /* skip one period */
    }
}

static void snd_pcm_file_add_frames(snd_pcm_t *pcm, 
				    const snd_pcm_channel_area_t *areas,
				    snd_pcm_uframes_t offset,
				    snd_pcm_uframes_t frames)
{
	snd_pcm_file_t *file = pcm->private_data;
	while (frames > 0) {
		snd_pcm_uframes_t n = frames;
		snd_pcm_uframes_t cont = file->wbuf_size - file->appl_ptr;
		snd_pcm_uframes_t avail = file->wbuf_size - snd_pcm_bytes_to_frames(pcm, file->wbuf_used_bytes);
		if (n > cont)
			n = cont;
		if (n > avail)
			n = avail;
		snd_pcm_areas_copy(file->wbuf_areas, file->appl_ptr, 
				   areas, offset,
				   pcm->channels, n, pcm->format);
		frames -= n;
		offset += n;
		file->appl_ptr += n;
		if (file->appl_ptr == file->wbuf_size)
			file->appl_ptr = 0;
		file->wbuf_used_bytes += snd_pcm_frames_to_bytes(pcm, n);
		if (file->wbuf_used_bytes > file->buffer_bytes)
			snd_pcm_file_write_bytes(pcm, file->wbuf_used_bytes - file->buffer_bytes);
		assert(file->wbuf_used_bytes < file->wbuf_size_bytes);
	}
}

int
sa_stream_drain(sa_stream_t *s)
{
  if (s == NULL || s->output_unit == NULL) {
    return SA_ERROR_NO_INIT;
  }

  if (snd_pcm_state(s->output_unit) == SND_PCM_STATE_PREPARED) {
    size_t min_samples = 0;
    size_t min_bytes = 0;
    void *buf;

    if (sa_stream_get_min_write(s, &min_samples) < 0)
      return SA_ERROR_SYSTEM;
    min_bytes = snd_pcm_frames_to_bytes(s->output_unit, min_samples);    

    buf = malloc(min_bytes);
    if (!buf)
      return SA_ERROR_SYSTEM;
    memset(buf, 0, min_bytes);
    sa_stream_write(s, buf, min_bytes);
    free(buf);
  }

  if (snd_pcm_state(s->output_unit) != SND_PCM_STATE_RUNNING) {
    return SA_ERROR_INVALID;
  }
  snd_pcm_drain(s->output_unit);
  return SA_SUCCESS;
}