[Speex-dev] Problems with the Speex Jitter Buffer

[Jean-Marc Valin]

David Feurle wrote:
> Thanks for your reply Jean-Marc!
> 
> this was what I had before.
> But I decided to restructure it since the thread that plays the sound is
> a callback from the sound hardware, more or less an interrupt handler.
> For me it seems more reasonable to waste some memory for to save the
> decompressed Packet. While I write this I begin to think that it is
> possible I decompress Packets that are never used because they are too
> late. What is the reason why one should put the compressed Packet in the
> JitterBuffer?

Because otherwise, you end up decoding the packets in random order --
not very useful with a stateful codec!

	Jean-Marc

>       David
>> (Sorry about the delay -- currently attending ICASSP)
>> Hi,
>>
>> Haven't looked at all the details, but what's clearly wrong is that you
>> need to put the *compressed* packets in the jitter buffer and decode
>> them only when you _get() them.
>>
>>     Jean-Marc
>>
>> David Feurle wrote:
>>  
>>> Hi,
>>>
>>> I am using the JitterBuffer. Since there is not so much documentation I
>>> think I dont use it in a correct way. All the packets are recieved (I
>>> control the sequence numbers) but the JitterBuffer often tells me he has
>>> no packet. I am using it in the following way:
>>>
>>> I am not sure if I use the ticks correctly but I think it can be set to
>>> 20(msec).
>>> It is set as a Member in my class and i pointed out where i use it so it
>>> is clear if i use it somewhere i better shouldnt.
>>>
>>> - I initialize the JitterBuffer with ticks = 20 (saved in the variable
>>> m_Ticks)
>>> - My network thread repeadedly (every 20msec) calls AddPacket() which
>>> adds the packet to the buffer
>>>          320 bytes of audio data are set as the data
>>>          the timestamp is set to the sequence number of the packet times
>>> 20 (m_Ticks)
>>>          the span of the packet is set to 20 (the packet covers one tick
>>> entirely)
>>> - A thread which plays my Audio calls every 20msec the function
>>> GetSound()
>>>
>>> As I said before the buffer just returns more or less the halve of the
>>> packets. But all the packets are added to the JitterBuffer.
>>> I posted some of the code i use in my email and i would be really
>>> thankfull if anybody could tell me where i am using the JitterBuffer
>>> wrong.
>>>
>>> Many thanks in advance
>>>
>>> David Feurle
>>>
>>>
>>>
>>> Init()
>>> {
>>>    m_JitterBuffer = jitter_buffer_init(m_Ticks);
>>>    jitter_buffer_reset(m_JitterBuffer);
>>> }
>>>
>>> Exit()
>>> {
>>>        jitter_buffer_destroy(m_JitterBuffer);
>>> }
>>>
>>> void BeatJitterBuffer::AddPacket(Packet* packet)
>>> {
>>>    m_Mutex.Aquire();
>>>          char buff[320];
>>>        JitterBufferPacket p;
>>>        m_Decoder->DecompressPacket(packet, buff, 320);
>>>        p.data = buff;
>>>        p.len = 320;
>>>        p.timestamp = packet->SequenceNumber() * m_Ticks;
>>>        p.span = m_Ticks;
>>>        jitter_buffer_put(m_JitterBuffer, &p);
>>>    }
>>>
>>>    m_Mutex.Release();
>>>    delete packet;
>>> }
>>>
>>> void BeatJitterBuffer::GetSound(char* buffer, size_t maxLength)
>>> {
>>>    int ret;
>>>
>>>    if (320 == maxLength)
>>>    {
>>>        JitterBufferPacket packet;
>>>        packet.data = buffer;
>>>
>>>        m_Mutex.Aquire();
>>>
>>>        ret = jitter_buffer_get(m_JitterBuffer, &packet, 0);
>>>
>>>        if(ret != JITTER_BUFFER_OK)
>>>        {
>>>            ZeroMemory(packet.data, maxLength);
>>>         }
>>>
>>>        jitter_buffer_tick(m_JitterBuffer);
>>>        jitter_buffer_update_delay(m_JitterBuffer, &packet, NULL);
>>>        m_Mutex.Release();
>>>    }
>>>    else
>>>    {
>>>        ZeroMemory(buffer, maxLength);
>>>    }
>>> }
>>>
>>> _______________________________________________
>>> Speex-dev mailing list
>>> Speex-dev at xiph.org
>>> http://lists.xiph.org/mailman/listinfo/speex-dev
>>>
>>>     
> 
>