[FFmpeg-devel] [PATCH 1/1] avdevice/decklink_dec: Autodetect the video input format

[Marton Balint]

On Thu, 16 Nov 2017, Jeyapal, Karthick wrote:

>> On 11/16/17, 1:11 AM, "Marton Balint" <cus at passwd.hu> wrote:
>
> Thanks for the reply.
>
>> For the first patch, I think you forgot to call ff_decklink_set_configs in
>> decklink_enc.
> ff_decklink_set_configs is not doing anything related to decklink_enc
> In any case I have added the same and have attached the new patch
>
>> For the second patch here are some comments:
> I have done all suggested modifications and the new patch is attached.

Thanks, there is one more thing I still don't get:

[...]

> -static HRESULT decklink_start_input(AVFormatContext *avctx)
> -{
> -    struct decklink_cctx *cctx = (struct decklink_cctx *)avctx->priv_data;
> +static int decklink_autodetect(struct decklink_cctx *cctx) {
>      struct decklink_ctx *ctx = (struct decklink_ctx *)cctx->ctx;
> +    DECKLINK_BOOL autodetect_supported = false;
> +    int i;
> +
> +    if (ctx->attr->GetFlag(BMDDeckLinkSupportsInputFormatDetection, &autodetect_supported) != S_OK)
> +        return -1;
> +    if (autodetect_supported == false)
> +        return -1;
> +
> +    ctx->autodetect = 1;
> +    ctx->bmd_mode  = bmdModeUnknown;
> +    if (ctx->dli->EnableVideoInput(AUTODETECT_DEFAULT_MODE,
> +                                   bmdFormat8BitYUV,
> +                                   bmdVideoInputEnableFormatDetection) != S_OK) {
> +        return -1;
> +    }
> +
> +    if (ctx->dli->StartStreams() != S_OK) {
> +        return -1;
> +    }
> +
> +    // 1 second timeout
> +    for (i = 0; i < 10; i++) {
> +        av_usleep(100000);
> +        // Sometimes VideoInputFrameArrived is called before VideoInputFormatChanged
> +        // So don't break for bmd_mode == AUTODETECT_DEFAULT_MODE

Even if you get a frame for the default mode, and 
VideoInputFrameArrived is called early, the bmdFrameHasNoInputSource 
flag should be set, so ctx->bmd_mode remains unknown, therefore you don't 
have to handle it specially.

Are you saying that the Decklink drivers are buggy, and there are cases 
where you get a frame without the bmdFrameHasNoInputSource flag, and then 
a VideoInputFormatChanged callback later?

> +        if (ctx->bmd_mode != bmdModeUnknown &&
> +            ctx->bmd_mode != AUTODETECT_DEFAULT_MODE)
> +            break;
> +    }
> +

[...]

Regards,
Marton