[FFmpeg-devel] [PATCH v2 08/11] vaapi_encode_mjpeg: Warn if input is not full range

Carl Eugen Hoyos ceffmpeg at gmail.com
Sun Feb 10 20:49:39 EET 2019

2019-02-10 19:21 GMT+01:00, Mark Thompson <sw at jkqxz.net>:
> On 05/02/2019 13:27, Carl Eugen Hoyos wrote:
>> 2019-01-28 0:47 GMT+01:00, Mark Thompson <sw at jkqxz.net>:
>>> +    if (avctx->color_range == AVCOL_RANGE_MPEG) {
>>> +        av_log(avctx, AV_LOG_WARNING, "Input video does not appear "
>>> +               "to use full-range: output colours may be incorrect.\n");
>> The wording seems not ideal to me:
>> Are you not sure if the encoder will produce correct output for
>> mpeg-range jpeg?
>> That's how it sounds to me...
> The problem is that, unlike H.264 and other codecs, JPEG has no way to
> signal that the data are actually limited-range.  The encode will preserve
> the values, but those values will not have the right interpretation at a
> remote end which only looks at the JPEG data.  On the other hand, if
> signalled by some out-of-band method (perhaps the container, or you control
> both ends) everything is perfectly usable.
> I agree the message isn't particularly clear; do you have any thoughts about
> how it should be phrased?

Can't you add the same COM tag as mjpegenc_common.c does?

If not it could be something like "mpeg-range jpeg will be undetectable".

Carl Eugen

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