On Tue, Feb 27, 2024 at 09:14:04PM +0800, Zhao Zhili wrote: > > > > On Feb 27, 2024, at 15:17, Matthieu Bouron <matthieu.bou...@gmail.com> > > wrote: > > > > On Sat, Feb 24, 2024 at 12:29:24PM +0100, Matthieu Bouron wrote: > >> On Thu, Feb 15, 2024 at 10:13:03AM +0100, Matthieu Bouron wrote: > >>> Le jeu. 15 févr. 2024, 9:46 AM, Zhao Zhili <quinkbl...@foxmail.com> a > >>> écrit : > >>> > >>>> > >>>>> 在 2024年2月15日,下午3:57,Matthieu Bouron <matthieu.bou...@gmail.com> 写道: > >>>>> > >>>>> On Thu, Feb 15, 2024 at 12:13:59PM +0800, Zhao Zhili wrote: > >>>>>> > >>>>>> > >>>>>>>> On Feb 14, 2024, at 06:50, Matthieu Bouron > >>>>>>>> <matthieu.bou...@gmail.com> > >>>> wrote: > >>>>>>> > >>>>>>> Hi, > >>>>>>> > >>>>>>> On Android, content providers are used for accessing files through > >>>> shared > >>>>>>> mechanisms. One typical case would be an app willing to open a video > >>>> from > >>>>>>> Google Photos, gallery apps, TikTok, Instagram or some other > >>>>>>> providers. > >>>>>>> A content URI looks something like "content://authority/path/id", see: > >>>>>>> https://developer.android.com/reference/android/content/ContentUris > >>>>>>> > >>>> https://developer.android.com/guide/topics/providers/content-provider-basics > >>>>>>> > >>>>>>> It can currently be somehow managed through clumsy means such as using > >>>> a "fd:" > >>>>>>> filename and crafting a special AVOption, which also has the drawback > >>>> of > >>>>>>> requiring the third party to carry around opened file descriptors > >>>> (with the > >>>>>>> multiple opened file limitations implied). Custom AVIOContexts are > >>>> also an > >>>>>> > >>>>>> File descriptor is a general abstraction layer, it target more > >>>> platforms than > >>>>>> Android specific content provider. Android provided getFd() API since > >>>> API > >>>>>> level 12, I guess that’s the default method to deal with content > >>>> provider in > >>>>>> native code. It’s a few lines of code to get native fd in Java, but > >>>> dozens of code > >>>>>> in C with JNI, which is what this patchset done. > >>>>>> > >>>>>> For multiple opened file limitations issue, they can close the file > >>>> descriptor after > >>>>>> open. It’s unlikely to reach the limit in normal case without leak. > >>>>>> > >>>>>> I’m OK to provide this android_content_protocol helper if user > >>>>>> requests. > >>>>> > >>>>> I've been doing this kind of work for 3/4 users (including myself) at > >>>> this > >>>>> point and have to do it another time, this is what motivated me to > >>>> propose > >>>>> this patchset. > >>>>> > >>>>>> > >>>>>>> option. Both options will have to deal with the JNI though and end > >>>> users will > >>>>>>> have to re-implement the same exact thing. > >>>>>> > >>>>>> User still need to deal with JNI with the new android_content_protocol, > >>>> more or > >>>>>> less, it’s unavoidable. > >>>>> > >>>>> The advantage I see of using this protocol is that the user only need to > >>>>> call av_jni_set_jvm() + av_jni_set_android_app_ctx() at the start of the > >>>>> application and FFmpeg will handle the content-uri transparently. This > >>>>> is > >>>>> especially helpful if the Android application rely on multiple libraries > >>>>> that in turn rely on FFmpeg to read medias. > >>>> > >>>> The url still need to be passed from Java to C via JNI, it’s not much > >>>> different compared to pass fd. > >>>> > >>> > >>> It's not that much different I agree. But let's say you have a rendering > >>> engine (in C) where you need to pass hundreds of media (from the user) to > >>> render a scene, each media is used at different time during the rendering. > >>> And Ffmpeg is not a direct dependency and can be called from different > >>> libraries/places used by the rendering engine. Calling > >>> av_jni_set_android_app_ctx() and you're done, you can pass the content URI > >>> to the engine (passing fd at this stage is not an option imho). You still > >>> need to convert the uri from java string to c before calling the c code, > >>> but it's a direct translation which is typically part of a binding. > >>> > >>> > >>> > >>>>> > >>>>>> > >>>>>>> > >>>>>>> This patchset addresses this by adding a content provider protocol, > >>>> which has > >>>>>>> an API fairly similar to fopen. Android 11 appears to provide > >>>>>>> something > >>>>>>> transparent within fopen(), but FFmpeg doesn't use it in the file > >>>> protocol, and > >>>>>>> Android < 11 are still widely used. > >>>>>>> > >>>>>>> The first part move the JNI infrastructure from avcodec to avutil (it > >>>> remains > >>>>>>> internally shared, there is little user implication), > >>>>>> > >>>>>> OK. JNI infrastructure should belong to avutil at the first place, so > >>>> hwcontext_mediacodec > >>>>>> and so on can use it. Unfortunately for those new avpriv_. > >>>>> > >>>>> What do you mean by "Unfortunately" ? Would you like to make the JNI API > >>>>> public ? > >>>> > >>>> I think it’s our target to reduce the number of avpriv API, not increase > >>>> it. Does duplicate the compile unit work in this case so we don’t need to > >>>> export the symbols? > >>>> > >>> > >>> Directly including ffjni.c from libavformat/file.c works. We still need to > >>> pass the application context though (could be added to avcodec/jni.h) > >> > >> So what would be the preferred way forward ? including libavformat/file.c > >> or > >> migrating the code to avutil (avpriv_*) ? > > > > Ping (sorry to ping this early, I'd like to not miss the 7.0 window, > > especially if we choose the avpriv_ route). > > I prefer the solution to dup compile unit and use as less avpriv_ as possible.
Thanks. I'll adjust the patchset accordingly. [...] _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".