2012-11-03 17:19, Colin Guthrie skrev: > 'Twas brillig, and Tanu Kaskinen at 05/10/12 13:58 did gyre and gimble: >> On Wed, 2012-10-03 at 08:50 +0200, David Henningsson wrote: >>> On 10/02/2012 10:38 PM, Tanu Kaskinen wrote: >>>> On Mon, 2012-10-01 at 17:06 +0200, David Henningsson wrote: >>>>> If there is no silence memblock and no data, pa_memblockq_peek can >>>>> return NULL. In this case, do not crash on an assertion in >>>>> pa_memblock_acquire, but instead return a proper error to the client. >>>> If there is no data in the buffer, pa_stream_peek() is supposed to >>>> return NULL according to the documentation. And it does that: if there's >>>> no data, pa_memblock_peek() will return a negative value, causing >>>> pa_stream_peek() to return NULL. >>>> >>>> The problem is the case where the buffer does contain data, but not at >>>> the read index. That is, there is a hole in the buffer. The client >>>> documentation doesn't have any warnings about holes, so the only safe >>>> way to handle holes is to return silence. Fixing this should be a simple >>>> matter of giving a silence memchunk when creating record_memblockq. >>> I'm not so sure. Silence, as in all zeroes, might work for S16 audio >>> data, but what about other formats? Compressed audio? Peak audio (which >>> I think is the case here)? Etc. >> Good point. Regarding PCM, if pa_memchunk_silence() is used, the >> function will take care of filling the memory with appropriate content. >> But that doesn't work with compressed audio. >> >>> Also maybe it could also be valuable for the client to distinguish >>> between no data available, and valid zero data. >>> >>> How about returning NULL and adding to the documentation something like: >>> >>> -If no data is available this will return a NULL pointer. >>> +If no data is available (at the current read position), this will >>> return a NULL pointer. >> An addition: the client probably wants to know how large the hole is. It >> might be possible to figure that out somehow from the read index, but I >> think it would make sense to return the hole size in the length >> parameter. > This discussion seemed to stagnate. Is this worth fixing/documenting for > the 3.0 release? > > Col > > Returning NULL seems to be the right thing to do here, even if gnome-control-center does not handle that very well IIRC. So we might need an additional patch in g-c-c. So assuming I commit a patch doing that. If somebody else wants to add logic to figure out how large the hole is, that could be discussed separately. Any objections? -- David Henningsson, Canonical Ltd. https://launchpad.net/~diwic
