[FFmpeg-devel] [PATCHv3 4/4] libavcodec: v4l2: add support for v4l2 mem2mem codecs

[Jorge Ramirez]

On 08/04/2017 01:51 PM, Mark Thompson wrote:
>> +        break;
>> +    case AV_CODEC_ID_H263:
>> +        qmin = MPEG_CID(H263_MIN_QP);
>> +        qmax = MPEG_CID(H263_MAX_QP);
>> +        break;
>> +    case AV_CODEC_ID_VP8:
>> +    case AV_CODEC_ID_VP9:
>> +        qmin = MPEG_CID(VPX_MIN_QP);
>> +        qmax = MPEG_CID(VPX_MAX_QP);
>> +        break;
>> +    default:
>> +        return 0;
>> +    }
>> +
>> +    SET_V4L_EXT_CTRL(value, qmin, avctx->qmin, "minimum video quantizer scale");
>> +    SET_V4L_EXT_CTRL(value, qmax, avctx->qmax, "maximum video quantizer scale");
> The default values of qmin/qmax in options_table.h are set for the MPEG-4 part 2 encoder, and will do nasty things to others.  (Certainly for VP9 (assuming it maps to qindex) it's a very low value, so it probably won't ever get anywhere near the bitrate target for normal video.  H.26[45] and VP8 also, but to a lesser degree.)

would you know where can I get this information from (qmin/qmx for the 
other encoders)?