Hi Philipp, On Wed, Jul 25, 2018 at 10:28 PM Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> wrote: > > Hi Tomasz, > > On Tue, 2018-07-24 at 23:06 +0900, Tomasz Figa wrote: > > This series attempts to add the documentation of what was discussed > > during Media Workshops at LinuxCon Europe 2012 in Barcelona and then > > later Embedded Linux Conference Europe 2014 in Düsseldorf and then > > eventually written down by Pawel Osciak and tweaked a bit by Chrome OS > > video team (but mostly in a cosmetic way or making the document more > > precise), during the several years of Chrome OS using the APIs in > > production. > > > > Note that most, if not all, of the API is already implemented in > > existing mainline drivers, such as s5p-mfc or mtk-vcodec. Intention of > > this series is just to formalize what we already have. > > > > It is an initial conversion from Google Docs to RST, so formatting is > > likely to need some further polishing. It is also the first time for me > > to create such long RST documention. I could not find any other instance > > of similar userspace sequence specifications among our Media documents, > > so I mostly followed what was there in the source. Feel free to suggest > > a better format. > > > > Much of credits should go to Pawel Osciak, for writing most of the > > original text of the initial RFC. > > > > Changes since RFC: > > (https://lore.kernel.org/patchwork/project/lkml/list/?series=348588) > > - The number of changes is too big to list them all here. Thanks to > > a huge number of very useful comments from everyone (Philipp, Hans, > > Nicolas, Dave, Stanimir, Alexandre) we should have the interfaces much > > more specified now. The issues collected since previous revisions and > > answers leading to this revision are listed below. > > Thanks a lot for the update, and especially for the nice Q&A summary of > the discussions so far. > > [...] > > Decoder issues > > > [...] > > How should ENUM_FRAMESIZES be affected by profiles and levels? > > > > Answer: Not in current specification - the logic is too complicated and > > it might make more sense to actually handle this in user space. (In > > theory, level implies supported frame sizes + other factors.) > > For decoding I think it makes more sense to let the hardware decode them > from the stream and present them as read-only controls, such as: > > 42a68012e67c ("media: coda: add read-only h.264 decoder profile/level > controls") To clarify, this point is only about the effect on ENUM_FRAMESIZES. Profile and level controls are mentioned in capabilities enumeration, but it may make sense to add optional steps of querying them in Initialization sequence. > > if possible. For encoding, the coda firmware determines level from > bitrate and coded resolution, itself, so I agree not making this part of > the spec is a good idea for now. Encoder controls are driver-specific in general, since the encoding capabilities vary a lot, so I decided to just briefly mention the general idea of encoding parameters in "Encoding parameter changes" section. It could be a good idea to add a reference to the MPEG control documentation there, though. Best regards, Tomasz
