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  4. Qt Multimedia 6.7.2 with ffmpeg cannot decode h264 on Pi5

Qt Multimedia 6.7.2 with ffmpeg cannot decode h264 on Pi5

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  • D Offline
    D Offline
    Dragoner
    wrote on last edited by
    #1

    I am try to use a QMediaPlayer with QT_MEDIA_BACKEND=ffmpeg to play a video with h264 codec on a Rasperry Pi 5, but failing with the error:

    qt.core.plugin.factoryloader: checking directory path "/opt/Qt6.7.2/plugins/multimedia" ...
qt.core.plugin.factoryloader: looking at "/opt/Qt6.7.2/plugins/multimedia/libffmpegmediaplugin.so"
qt.core.plugin.loader: Found metadata in lib /opt/Qt6.7.2/plugins/multimedia/libffmpegmediaplugin.so, metadata=
{
    "IID": "org.qt-project.Qt.QPlatformMediaPlugin",
    "MetaData": {
        "Keys": [
            "ffmpeg"
        ]
    },
    "archlevel": 0,
    "className": "QFFmpegMediaPlugin",
    "debug": false,
    "version": 395008
}


qt.core.plugin.factoryloader: Got keys from plugin meta data QList("ffmpeg")
qt.core.plugin.factoryloader: checking directory path "/home/pi/repos/gainbridge-qt672/build/multimedia" ...
qt.core.library: "/opt/Qt6.7.2/plugins/multimedia/libffmpegmediaplugin.so" loaded library
[2024-11-28 12:31:58.731] [info] Setting video src=RedLeftToRight.avi
"FFmpeg log: Opening 'RedLeftToRight.avi' for reading"
"FFmpeg log: Setting default whitelist 'file,crypto,data'"
"FFmpeg log: Format avi probed with size=2048 and score=100"
"FFmpeg log: use odml:1"
"FFmpeg log: Before avformat_find_stream_info() pos: 5754 bytes read:22652 seeks:0 nb_streams:1"
"FFmpeg log: nal_unit_type: 7(SPS), nal_ref_idc: 3"
"FFmpeg log: nal_unit_type: 8(PPS), nal_ref_idc: 3"
"FFmpeg log: nal_unit_type: 6(SEI), nal_ref_idc: 0"
"FFmpeg log: nal_unit_type: 5(IDR), nal_ref_idc: 3"
"FFmpeg log: nal_unit_type: 7(SPS), nal_ref_idc: 3"
"FFmpeg log: nal_unit_type: 8(PPS), nal_ref_idc: 3"
"FFmpeg log: nal_unit_type: 6(SEI), nal_ref_idc: 0"
"FFmpeg log: nal_unit_type: 5(IDR), nal_ref_idc: 3"
"FFmpeg log: Format yuv422p chosen by get_format()."
"FFmpeg log: Reinit context to 208x80, pix_fmt: yuv422p"
"FFmpeg log: no picture "
"FFmpeg log: All info found"
"FFmpeg log: rfps: 29.666667 0.016451"
"FFmpeg log: rfps: 29.666667 0.016451"
"FFmpeg log: rfps: 29.750000 0.009253"
"FFmpeg log: rfps: 29.750000 0.009253"
"FFmpeg log: rfps: 29.833333 0.004113"
"FFmpeg log: rfps: 29.833333 0.004113"
"FFmpeg log: rfps: 29.916667 0.001028"
"FFmpeg log: rfps: 29.916667 0.001028"
"FFmpeg log: rfps: 30.000000 0.000000"
"FFmpeg log: rfps: 60.000000 0.000000"
"FFmpeg log: rfps: 120.000000 0.000000"
"FFmpeg log: rfps: 240.000000 0.000000"
"FFmpeg log: rfps: 29.970030 0.000133"
"FFmpeg log: rfps: 29.970030 0.000133"
"FFmpeg log: rfps: 59.940060 0.000532"
"FFmpeg log: rfps: 59.940060 0.000532"
"FFmpeg log: After avformat_find_stream_info() pos: 7767 bytes read:22652 seeks:0 frames:41"
"FFmpeg log: The input looks like it is Annex B already"
"FFmpeg log: nal_unit_type: 7(SPS), nal_ref_idc: 3"
"FFmpeg log: nal_unit_type: 8(PPS), nal_ref_idc: 3"
"FFmpeg log: probing device /dev/video20"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video21"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video22"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video19"
"FFmpeg log: driver 'rpivid' on card 'rpivid' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video23"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video24"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video25"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video26"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video27"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in unknown mode"
"FFmpeg log: probing device /dev/video28"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video29"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video30"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video31"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video32"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video33"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video34"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in mplane mode"
"FFmpeg log: v4l2 output format not supported"
"FFmpeg log: probing device /dev/video35"
"FFmpeg log: driver 'pispbe' on card 'pispbe' in unknown mode"
"FFmpeg log: Could not find a valid device"
"FFmpeg log: can't configure decoder"
"FFmpeg log: V4L2 Codec end"
"FFmpeg log: V4L2 Context destroyed"

    For me it looks like Qt or ffmpeg tries to use a hardware decoder which is not available on Pi5. I am expecting that ffmpeg/Qt should fall back to software decoding in that case.

    I first thought this might be a bug in ffmpeg, but I am able to convert that video to another codec successfully:

    ffmpeg -i RedLeftToRight.avi -c:v rawvideo raw.avi

    So, I assume ffmpeg is able to decode h264 without hardware encoder support.

    How can I get this running?

    1 Reply Last reply
    0
    • Nhan NguyenN Nhan Nguyen moved this topic from General and Desktop on
    • G Offline
      G Offline
      Graullon
      wrote on last edited by
      #2

      There are 2 possible reasons of why is it not working:

      1. Qt code issue, there is not enough checks if initialized v4l2 decoder can do its job properly.
      2. Your FFMPEG build issue. If I remember it right there is no built-in h264 decoder in FFMPEG, you need to built-in some third-party lib yourself. No software impl to fallback on.
      1 Reply Last reply
      0
      • C Offline
        C Offline
        CadErik
        wrote on last edited by
        #3

        I have a similar issue with an opi 5 (rk3588) and I can't get the hardware decoding to work at all. I am guessing that QT is using its own FFMPEG instead of the platform one.

        1 Reply Last reply
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