Hi, Zhao Liang-E3423C wrote: > Zhao Liang-E3423C wrote: > >> Hi all, >> >> On embedded device, DSP is used widely, many DSPs have different >> features, for example: >> >> 1. decoder >> DSP is just a hardware decoder >> 2. decoder + sink >> DSP is a decoder plus sink, it can directly accept encoded data, and >> then decode it and render pcm data into audio device directly. >> > > creating a sink with right caps should be enough for this one... > > Zhao Liang: By my experience, it is not simple like just adding a new > caps. > Just a example, how to handle preroll? Generally, dsp need to do > initialization when start to work, so what is the time to do this? > another issue is seek, how does DSP handle seek? > > >this is generally the demuxer/parser's job to handle seek, do you have examples where it is up to the decoder to do it ? As it is a sink for DSP although it includes decoder functions, sink would handle preroll, in current preroll mechanism, it only allows sink do once preroll virtual function, all other buffers are pushed into queue, but some hardwares need more buffers to do initialization. Another issue is if the DSP is audio decoder + sink, how to handle clock line increasing? Currently, we can use gstaudiosink to do it, gstringbuffer can handle all clock line increasing, but some DSP can not do it if no data is fed into, so the clock calculation is really a issue. If no mechanism, rtsp streaming application will not handle buffer delay or lost. >> 3. A/V sync >> DSP can do A/V sync internally or not. >> > > then you can ask basesink not to synchronize flows. > > Zhao Liang: If DSP is just a video decoder and sink, how does DSP sync > with audio sink? maybe current basesink considers more software sink > than hardware sink. > > >I was talking about your hardware handling A/V synchronization, not the opposite. >buffers that are handled by sink are timestamped (by demuxers for >instance) and are rightly handled by basesink when synchronization has to be done in framework, and not in HW. I understood your meaning, A/V sync is really done by basesink, but some DSPs also have internal buffers to store buffers synced. and these synced buffers are encoded buffers, not raw buffers. There are 4 combinations: 1. DSP videosink v.s software audiosink 2. DSP videosink v.s DSP audiosink 3. software videosink v.s DSP audiosink 4. software videosink v.s software audiosink How to sync a/v with encoded buffers? It really puzzled me. openmax can do it well for some cases, as it has a clock in itself. but by my understanding, basesink is used to sync decoded buffers. Appreicate for your clarifying. -- Benoit Fouet Purple Labs S.A. www.purplelabs.com
