• Takashi Sakamoto's avatar
    ALSA: firewire-lib: add replay target to cache sequence of packet · f9e5ecdf
    Takashi Sakamoto authored
    In design of audio and music unit in IEEE 1394 bus, feedback of
    effective sampling transfer frequency (STF) is delivered by packets
    transferred from device. The devices supported by ALSA firewire stack
    are categorized to three groups regarding to it.
    
     * Group 1:
       * Echo Audio Fireworks board module
       * Oxford Semiconductor OXFW971 ASIC
       * Digidesign Digi00x family
       * Tascam FireWire series
       * RME Fireface series
    
     * Group 2:
       * BridgeCo. DM1000/DM1100/DM1500 ASICs for BeBoB solution
       * TC Applied Technologies DICE ASICs
    
     * Group 3:
       * Mark of the Unicord FireWire series
    
    In group 1, the effective STF is determined by the sequence of the number
    of events per packet. In group 2, the sequence of presentation timestamp
    expressed in syt field of CIP header is interpreted as well. In group 3,
    the presentation timestamp is expressed in source packet header (SPH) of
    each data block.
    
    I note that some models doesn't take care of effective STF with large
    internal buffer. It's reasonable to name it as group 0:
    
     * Group 0
       * Oxford Semiconductor OXFW970 ASIC
    
    The effective STF is known to be slightly different from nominal STF for
    all of devices, and to be different between the devices. Furthermore, the
    effective STF is known to be shifted for long-period transmission. This
    makes it hard for software to satisfy the effective STF when processing
    packets to the device.
    
    The effective STF is deterministic as a result of analyzing the batch of
    packet transferred from the device. For the analysis, caching the sequence
    of parameter in the packet is required.
    
    This commit adds an option so that AMDTP domain structure takes AMDTP
    stream structure to cache the sequence of parameters in packet transferred
    from the device. The parameters are offset ticks of syt field against the
    cycle to receive the packet and the number of data blocks per packet.
    Signed-off-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
    Link: https://lore.kernel.org/r/20210527122611.173711-2-o-takashi@sakamocchi.jpSigned-off-by: default avatarTakashi Iwai <tiwai@suse.de>
    f9e5ecdf
tascam-stream.c 12.1 KB