On 8/3/2017 4:22 AM, Steinar H. Gunderson wrote:
> The height convention for decoding frames with only a single field made sense
> for compatibility with legacy decoders, but doesn't really match the
> convention
> used by NDI, which is the primary (only?) user. Thus, change it to simply
> assuming that if the two fields overlap, the frame is meant to be a single
> field and the frame height matches the field height.
> ---
> libavcodec/speedhq.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/libavcodec/speedhq.c b/libavcodec/speedhq.c
> index 60efb0222b..47b1e4dc7a 100644
> --- a/libavcodec/speedhq.c
> +++ b/libavcodec/speedhq.c
> @@ -450,10 +450,13 @@ static int speedhq_decode_frame(AVCodecContext *avctx,
> if (second_field_offset == 4) {
> /*
> * Overlapping first and second fields is used to signal
> - * encoding only a single field (the second field then comes
> - * as a separate, later frame).
> + * encoding only a single field. In this case, "height"
> + * is ambiguous; it could mean either the height of the
> + * frame as a whole, or of the field. The former would make
> + * more sense for compatibility with legacy decoders,
> + * but this matches the convention used in NDI, which is
> + * the primary user of this trick.
> */
> - frame->height >>= 1;
> if ((ret = decode_speedhq_field(s, buf, buf_size, frame, 0, 4,
> buf_size, 1)) < 0)
> return ret;
> } else {
>
Applied.
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