Re: [FFmpeg-devel] [PATCH v5 07/21] avdevice/avdevice: Revert "Deprecate AVDevice Capabilities API"

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Diederick Niehorster:
> This reverts commit 4f49ca7bbc75a9db4cdf93f27f95a668c751f160. The next
> few patches clean up the API and implement this capability for
> avdevice/dshow.
> 
> Bumping avformat and avdevice version.
> 
> Signed-off-by: Diederick Niehorster <dcnieho@gmail.com>
> ---
>  libavdevice/avdevice.c | 71 ++++++++++++++++++++++++++++++++++++++----
>  libavdevice/avdevice.h |  5 ---
>  libavdevice/version.h  |  4 +--
>  libavformat/avformat.h | 21 +++++++++++++
>  libavformat/version.h  |  2 +-
>  5 files changed, 89 insertions(+), 14 deletions(-)
> 
> diff --git a/libavdevice/avdevice.c b/libavdevice/avdevice.c
> index 43d3406670..d367189532 100644
> --- a/libavdevice/avdevice.c
> +++ b/libavdevice/avdevice.c
> @@ -28,11 +28,39 @@
>  #include "libavutil/ffversion.h"
>  const char av_device_ffversion[] = "FFmpeg version " FFMPEG_VERSION;
>  
> -#if FF_API_DEVICE_CAPABILITIES
> +#define E AV_OPT_FLAG_ENCODING_PARAM
> +#define D AV_OPT_FLAG_DECODING_PARAM
> +#define A AV_OPT_FLAG_AUDIO_PARAM
> +#define V AV_OPT_FLAG_VIDEO_PARAM
> +#define OFFSET(x) offsetof(AVDeviceCapabilitiesQuery, x)
> +
>  const AVOption av_device_capabilities[] = {
> +    { "codec", "codec", OFFSET(codec), AV_OPT_TYPE_INT,
> +        {.i64 = AV_CODEC_ID_NONE}, AV_CODEC_ID_NONE, INT_MAX, E|D|A|V },
> +    { "sample_format", "sample format", OFFSET(sample_format), AV_OPT_TYPE_SAMPLE_FMT,
> +        {.i64 = AV_SAMPLE_FMT_NONE}, AV_SAMPLE_FMT_NONE, INT_MAX, E|D|A },
> +    { "sample_rate", "sample rate", OFFSET(sample_rate), AV_OPT_TYPE_INT,
> +        {.i64 = -1}, -1, INT_MAX, E|D|A },
> +    { "channels", "channels", OFFSET(channels), AV_OPT_TYPE_INT,
> +        {.i64 = -1}, -1, INT_MAX, E|D|A },
> +    { "channel_layout", "channel layout", OFFSET(channel_layout), AV_OPT_TYPE_CHANNEL_LAYOUT,
> +        {.i64 = -1}, -1, INT_MAX, E|D|A },
> +    { "pixel_format", "pixel format", OFFSET(pixel_format), AV_OPT_TYPE_PIXEL_FMT,
> +        {.i64 = AV_PIX_FMT_NONE}, AV_PIX_FMT_NONE, INT_MAX, E|D|V },
> +    { "window_size", "window size", OFFSET(window_width), AV_OPT_TYPE_IMAGE_SIZE,
> +        {.str = NULL}, -1, INT_MAX, E|D|V },
> +    { "frame_size", "frame size", OFFSET(frame_width), AV_OPT_TYPE_IMAGE_SIZE,
> +        {.str = NULL}, -1, INT_MAX, E|D|V },
> +    { "fps", "fps", OFFSET(fps), AV_OPT_TYPE_RATIONAL,
> +        {.dbl = -1}, -1, INT_MAX, E|D|V },
>      { NULL }
>  };
> -#endif
> +
> +#undef E
> +#undef D
> +#undef A
> +#undef V
> +#undef OFFSET
>  
>  unsigned avdevice_version(void)
>  {
> @@ -81,18 +109,49 @@ int avdevice_dev_to_app_control_message(struct AVFormatContext *s, enum AVDevToA
>      return s->control_message_cb(s, type, data, data_size);
>  }
>  
> -#if FF_API_DEVICE_CAPABILITIES
>  int avdevice_capabilities_create(AVDeviceCapabilitiesQuery **caps, AVFormatContext *s,
>                                   AVDictionary **device_options)
>  {
> -    return AVERROR(ENOSYS);
> +    int ret;
> +    av_assert0(s && caps);
> +    av_assert0(s->iformat || s->oformat);
> +    if ((s->oformat && !s->oformat->create_device_capabilities) ||
> +        (s->iformat && !s->iformat->create_device_capabilities))
> +        return AVERROR(ENOSYS);
> +    *caps = av_mallocz(sizeof(**caps));
> +    if (!(*caps))
> +        return AVERROR(ENOMEM);
> +    (*caps)->device_context = s;
> +    if (((ret = av_opt_set_dict(s->priv_data, device_options)) < 0))
> +        goto fail;
> +    if (s->iformat) {
> +        if ((ret = s->iformat->create_device_capabilities(s, *caps)) < 0)
> +            goto fail;
> +    } else {
> +        if ((ret = s->oformat->create_device_capabilities(s, *caps)) < 0)
> +            goto fail;
> +    }
> +    av_opt_set_defaults(*caps);
> +    return 0;
> +  fail:
> +    av_freep(caps);
> +    return ret;
>  }
>  
>  void avdevice_capabilities_free(AVDeviceCapabilitiesQuery **caps, AVFormatContext *s)
>  {
> -    return;
> +    if (!s || !caps || !(*caps))
> +        return;
> +    av_assert0(s->iformat || s->oformat);
> +    if (s->iformat) {
> +        if (s->iformat->free_device_capabilities)
> +            s->iformat->free_device_capabilities(s, *caps);
> +    } else {
> +        if (s->oformat->free_device_capabilities)
> +            s->oformat->free_device_capabilities(s, *caps);
> +    }
> +    av_freep(caps);
>  }
> -#endif
>  
>  int avdevice_list_devices(AVFormatContext *s, AVDeviceInfoList **device_list)
>  {
> diff --git a/libavdevice/avdevice.h b/libavdevice/avdevice.h
> index 74e9518a8e..9724e7edf5 100644
> --- a/libavdevice/avdevice.h
> +++ b/libavdevice/avdevice.h
> @@ -347,7 +347,6 @@ int avdevice_dev_to_app_control_message(struct AVFormatContext *s,
>                                          enum AVDevToAppMessageType type,
>                                          void *data, size_t data_size);
>  
> -#if FF_API_DEVICE_CAPABILITIES
>  /**
>   * Following API allows user to probe device capabilities (supported codecs,
>   * pixel formats, sample formats, resolutions, channel counts, etc).
> @@ -443,7 +442,6 @@ typedef struct AVDeviceCapabilitiesQuery {
>  /**
>   * AVOption table used by devices to implement device capabilities API. Should not be used by a user.
>   */
> -attribute_deprecated
>  extern const AVOption av_device_capabilities[];
>  
>  /**
> @@ -463,7 +461,6 @@ extern const AVOption av_device_capabilities[];
>   *
>   * @return >= 0 on success, negative otherwise.
>   */
> -attribute_deprecated
>  int avdevice_capabilities_create(AVDeviceCapabilitiesQuery **caps, AVFormatContext *s,
>                                   AVDictionary **device_options);
>  
> @@ -473,9 +470,7 @@ int avdevice_capabilities_create(AVDeviceCapabilitiesQuery **caps, AVFormatConte
>   * @param caps Device capabilities data to be freed.
>   * @param s    Context of the device.
>   */
> -attribute_deprecated
>  void avdevice_capabilities_free(AVDeviceCapabilitiesQuery **caps, AVFormatContext *s);
> -#endif
>  
>  /**
>   * Structure describes basic parameters of the device.
> diff --git a/libavdevice/version.h b/libavdevice/version.h
> index e2c8757b27..7c132f2174 100644
> --- a/libavdevice/version.h
> +++ b/libavdevice/version.h
> @@ -30,8 +30,8 @@
>  
>  #include "version_major.h"
>  
> -#define LIBAVDEVICE_VERSION_MINOR   8
> -#define LIBAVDEVICE_VERSION_MICRO 101
> +#define LIBAVDEVICE_VERSION_MINOR   9
> +#define LIBAVDEVICE_VERSION_MICRO 100
>  
>  #define LIBAVDEVICE_VERSION_INT AV_VERSION_INT(LIBAVDEVICE_VERSION_MAJOR, \
>                                                 LIBAVDEVICE_VERSION_MINOR, \
> diff --git a/libavformat/avformat.h b/libavformat/avformat.h
> index 06db024559..027a914e13 100644
> --- a/libavformat/avformat.h
> +++ b/libavformat/avformat.h
> @@ -617,6 +617,16 @@ typedef struct AVOutputFormat {
>       * @see avdevice_list_devices() for more details.
>       */
>      int (*get_device_list)(struct AVFormatContext *s, struct AVDeviceInfoList *device_list);
> +    /**
> +     * Initialize device capabilities submodule.
> +     * @see avdevice_capabilities_create() for more details.
> +     */
> +    int (*create_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
> +    /**
> +     * Free device capabilities submodule.
> +     * @see avdevice_capabilities_free() for more details.
> +     */
> +    int (*free_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
>      enum AVCodecID data_codec; /**< default data codec */
>      /**
>       * Initialize format. May allocate data here, and set any AVFormatContext or
> @@ -797,6 +807,17 @@ typedef struct AVInputFormat {
>       */
>      int (*get_device_list)(struct AVFormatContext *s, struct AVDeviceInfoList *device_list);
>  
> +    /**
> +     * Initialize device capabilities submodule.
> +     * @see avdevice_capabilities_create() for more details.
> +     */
> +    int (*create_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
> +
> +    /**
> +     * Free device capabilities submodule.
> +     * @see avdevice_capabilities_free() for more details.
> +     */
> +    int (*free_device_capabilities)(struct AVFormatContext *s, struct AVDeviceCapabilitiesQuery *caps);
>  } AVInputFormat;
>  /**
>   * @}
> diff --git a/libavformat/version.h b/libavformat/version.h
> index d195704a31..88d6f750a2 100644
> --- a/libavformat/version.h
> +++ b/libavformat/version.h
> @@ -32,7 +32,7 @@
>  
>  #include "version_major.h"
>  
> -#define LIBAVFORMAT_VERSION_MINOR  22
> +#define LIBAVFORMAT_VERSION_MINOR  23
>  #define LIBAVFORMAT_VERSION_MICRO 100
>  
>  #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \

I have not really looked at the actual content of your dshow patches (as
I know nothing about dshow). But I really don't like the thought that
something is added to AVInput/OutputFormat that only a tiny fraction of
all (de)muxers will likely ever use. I think it would be more efficient
to add a single callback for the seldomly used types of callback like this:

int (*generic_callback)(struct AVFormatContext *s, int type, void
*priv1, void *priv2, int64_t num)

The uses of priv1, priv2 (and whether they are used at all) would depend
upon the type; they can be pointers to structures (which structures
depends upon type) to allow passing more arguments than otherwise
possible by the signature of generic_callback. type should actually be
an enum, but one can't forward declare an enum, so as long as the
internals are in public headers it won't be an enum.

The typical implementation of such a callback would be with a switch:

static int generic_callback(AVFormatContext *s, int type, void *priv1,
void *priv2, int64_t num)
{
    switch (type) {
    case FOO:
        return handle_foo(s, priv1, priv2, num);
    case BAR:
        return handle_bar(s, priv1, priv2, num);
    default:
        return AVERROR(ENOSYS);
}

The typical calling code would look like this:

{
    if (!s->oformat->generic_callback)
        AVERROR(ENOSYS);
    /* In case this type needs so many arguments that
     * a structure for them is used they should be prepared here. */
    ret = s->oformat->generic_callback(s, type_foo, /* other arguments);
    /* Inspect ret or just return it; notice that ret may very well be
AVERROR(ENOSYS) again, because the existence of the generic callback
does not imply that every type is supported. */
}

There are more callbacks that should be moved into this generic callback
besides the callbacks that you intend to add: The read_play and
read_pause callbacks which are only supported by a single demuxer. E.g.
av_read_play would look like this:

int av_read_play(AVFormatContext *s)
{
    if (s->iformat->generic_callback) {
        int ret = s->iformat->generic_callback(s, FF_CB_TYPE_READ_PLAY,
NULL, NULL, 0);
        if (ret != AVERROR(ENOSYS))
            return ret;
    }
    if (s->pb)
        return avio_pause(s->pb, 0);
    return AVERROR(ENOSYS);
}

- Andreas
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