On 07/08/17 19:51, Jorge Ramirez wrote: > 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)?
From the relevant language standards. H.263 / MPEG-4 part 2: [1, 31] (<https://www.itu.int/rec/T-REC-H.263>: PQUANT, GQUANT.) H.264 / MPEG-4 part 10 / AVC: [48 - 6 * bitdepth, 51] (<https://www.itu.int/rec/T-REC-H.264>: QpBdOffsety, pic_init_qp_minus26, slice_qp_delta.) H.265 / MPEG-H part 2 / HEVC: [48 - 6 * bitdepth, 51] (<https://www.itu.int/rec/T-REC-H.265>: QpBdOffsety, init_qp_minus26, slice_qp_delta.) VP8: [0, 127] (<https://tools.ietf.org/html/rfc6386>: q_index.) VP9: [0, 255] (<https://storage.googleapis.com/downloads.webmproject.org/docs/vp9/vp9-bitstream-specification-v0.6-20160331-draft.pdf>: base_q_idx.) - Mark _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
