[FFmpeg-trac] #11163(avdevice:new): avdevice_list_input_sources for dshow fails on machines with no video capture devices.

[FFmpeg]

#11163: avdevice_list_input_sources for dshow fails on machines with no video
capture devices.
----------------------------------+---------------------------------------
             Reporter:  Rishi     |                     Type:  enhancement
               Status:  new       |                 Priority:  normal
            Component:  avdevice  |                  Version:  6.1.1
             Keywords:            |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
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 Summary of the bug: avdevice_list_input_sources fails on machines with no
 video capture devices. While this sounds like by design, there are some
 machines with audio only capture devices, which an api user can then
 filter through.

 How to reproduce:
 It requires a Windows machine with no video capture devices.
     const AVInputFormat* inputFormat = av_find_input_format("dshow");
     AVDeviceInfoList* p;
     __FFmpegReturnFalseIfFail(avdevice_list_input_sources(inputFormat,
 nullptr, nullptr, &p));

 This stems from here libavdevice/dshow.c

     ret = dshow_cycle_devices(avctx, devenum, VideoDevice,
 VideoSourceDevice, NULL, NULL, &device_list);

     if (ret < S_OK)
         goto error;
     ret = dshow_cycle_devices(avctx, devenum, AudioDevice,
 AudioSourceDevice, NULL, NULL, &device_list);

 From https://learn.microsoft.com/en-us/previous-versions/ms784969(v=vs.85)
 ICreateDevEnum::CreateClassEnumerator returns S_FALSE if the category does
 not exist ...
 So why not cycle the audio devices if the video category does not exist,
 ie if specifically S_FALSE is returned. Happy to put in a patch, but does
 this sound like a right ask?
 My main scenario is to capture Stereo Mix Audio or any other recording
 devices.
 I am using this in my binary linked against FFmpeg 6_1 that I build on my
 own.

 $ git log -1
 commit 36126e4c142e43cc703f4b8c535d388ac5e403a4 (HEAD -> master)
 Author: Michael Niedermayer <michael at niedermayer.cc>
 Date:   Fri May 3 23:25:10 2024 +0200

     avcodec/exr: Fix preview overflow

     Fixes: CID1515456 Unintentional integer overflow

     Sponsored-by: Sovereign Tech Fund
     Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

 rishi at DESKTOP-0NQHKQI MINGW64 ~/localgitrepos/ffmpeg (master)
 $ git branch -vv
 * master 36126e4c14 [origin/master: behind 1596] avcodec/exr: Fix preview
 overflow
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/11163>
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