avconv: What are the mpegvideo private options?
Private options are switches/flags only applicable to specific encoders or decoders, and ignored by anything else.

To see the available private options for an encoder, use avconv -h encoder=name e.g. avconv -h encoder=flv

For LibAV, these are the private options available for the MPEG-1 &amp; 2 encoders.

{ "mpv_flags",      "Flags common for all mpegvideo-based encoders.", FF_MPV_OFFSET(mpv_flags), AV_OPT_TYPE_FLAGS, { .i64 = 0 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS, "mpv_flags" },\
{ "skip_rd",        "RD optimal MB level residual skipping", 0, AV_OPT_TYPE_CONST, { .i64 = FF_MPV_FLAG_SKIP_RD },    0, 0, FF_MPV_OPT_FLAGS, "mpv_flags" },\
{ "strict_gop",     "Strictly enforce gop size",             0, AV_OPT_TYPE_CONST, { .i64 = FF_MPV_FLAG_STRICT_GOP }, 0, 0, FF_MPV_OPT_FLAGS, "mpv_flags" },\
{ "qp_rd",          "Use rate distortion optimization for qp selection", 0, AV_OPT_TYPE_CONST, { .i64 = FF_MPV_FLAG_QP_RD },  0, 0, FF_MPV_OPT_FLAGS, "mpv_flags" },\
{ "cbp_rd",         "use rate distortion optimization for CBP",          0, AV_OPT_TYPE_CONST, { .i64 = FF_MPV_FLAG_CBP_RD }, 0, 0, FF_MPV_OPT_FLAGS, "mpv_flags" },\
{ "naq",            "normalize adaptive quantization",                   0, AV_OPT_TYPE_CONST, { .i64 = FF_MPV_FLAG_NAQ },    0, 0, FF_MPV_OPT_FLAGS, "mpv_flags" },\
{ "mv0",            "always try a mb with mv=&lt;0,0&gt;",                     0, AV_OPT_TYPE_CONST, { .i64 = FF_MPV_FLAG_MV0 },    0, 0, FF_MPV_OPT_FLAGS, "mpv_flags" },\
{ "luma_elim_threshold",   "single coefficient elimination threshold for luminance (negative values also consider dc coefficient)",\
                                                                      FF_MPV_OFFSET(luma_elim_threshold), AV_OPT_TYPE_INT, { .i64 = 0 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS },\
{ "chroma_elim_threshold", "single coefficient elimination threshold for chrominance (negative values also consider dc coefficient)",\
                                                                      FF_MPV_OFFSET(chroma_elim_threshold), AV_OPT_TYPE_INT, { .i64 = 0 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS },\
{ "quantizer_noise_shaping", NULL,                                  FF_MPV_OFFSET(quantizer_noise_shaping), AV_OPT_TYPE_INT, { .i64 = 0 },       0, INT_MAX, FF_MPV_OPT_FLAGS },\
{ "error_rate", "Simulate errors in the bitstream to test error concealment.",                                                                                                  \
                                                                    FF_MPV_OFFSET(error_rate),              AV_OPT_TYPE_INT, { .i64 = 0 },       0, INT_MAX, FF_MPV_OPT_FLAGS },\
{"qsquish", "how to keep quantizer between qmin and qmax (0 = clip, 1 = use differentiable function)",                                                                          \
                                                                    FF_MPV_OFFSET(rc_qsquish), AV_OPT_TYPE_FLOAT, {.dbl = 0 }, 0, 99, FF_MPV_OPT_FLAGS},                        \
{"rc_qmod_amp", "experimental quantizer modulation",                FF_MPV_OFFSET(rc_qmod_amp), AV_OPT_TYPE_FLOAT, {.dbl = 0 }, -FLT_MAX, FLT_MAX, FF_MPV_OPT_FLAGS},           \
{"rc_qmod_freq", "experimental quantizer modulation",               FF_MPV_OFFSET(rc_qmod_freq), AV_OPT_TYPE_INT, {.i64 = 0 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS},             \
{"rc_eq", "Set rate control equation. When computing the expression, besides the standard functions "                                                                           \
          "defined in the section 'Expression Evaluation', the following functions are available: "                                                                             \
          "bits2qp(bits), qp2bits(qp). Also the following constants are available: iTex pTex tex mv "                                                                           \
          "fCode iCount mcVar var isI isP isB avgQP qComp avgIITex avgPITex avgPPTex avgBPTex avgTex.",                                                                         \
                                                                    FF_MPV_OFFSET(rc_eq), AV_OPT_TYPE_STRING,                           .flags = FF_MPV_OPT_FLAGS },            \
{"rc_init_cplx", "initial complexity for 1-pass encoding",          FF_MPV_OFFSET(rc_initial_cplx), AV_OPT_TYPE_FLOAT, {.dbl = 0 }, -FLT_MAX, FLT_MAX, FF_MPV_OPT_FLAGS},       \
{"rc_buf_aggressivity", "currently useless",                        FF_MPV_OFFSET(rc_buffer_aggressivity), AV_OPT_TYPE_FLOAT, {.dbl = 1.0 }, -FLT_MAX, FLT_MAX, FF_MPV_OPT_FLAGS}, \
{"border_mask", "increase the quantizer for macroblocks close to borders", FF_MPV_OFFSET(border_masking), AV_OPT_TYPE_FLOAT, {.dbl = 0 }, -FLT_MAX, FLT_MAX, FF_MPV_OPT_FLAGS},    \
{"lmin", "minimum Lagrange factor (VBR)",                           FF_MPV_OFFSET(lmin), AV_OPT_TYPE_INT, {.i64 =  2*FF_QP2LAMBDA }, 0, INT_MAX, FF_MPV_OPT_FLAGS },            \
{"lmax", "maximum Lagrange factor (VBR)",                           FF_MPV_OFFSET(lmax), AV_OPT_TYPE_INT, {.i64 = 31*FF_QP2LAMBDA }, 0, INT_MAX, FF_MPV_OPT_FLAGS },            \
{"ibias", "intra quant bias",                                       FF_MPV_OFFSET(intra_quant_bias), AV_OPT_TYPE_INT, {.i64 = FF_DEFAULT_QUANT_BIAS }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS },   \
{"pbias", "inter quant bias",                                       FF_MPV_OFFSET(inter_quant_bias), AV_OPT_TYPE_INT, {.i64 = FF_DEFAULT_QUANT_BIAS }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS },   \
{"rc_strategy", "ratecontrol method",                               FF_MPV_OFFSET(rc_strategy), AV_OPT_TYPE_INT, {.i64 = 0 }, 0, 1, FF_MPV_OPT_FLAGS },   \
{"motion_est", "motion estimation algorithm",                       FF_MPV_OFFSET(motion_est), AV_OPT_TYPE_INT, {.i64 = FF_ME_EPZS }, FF_ME_ZERO, FF_ME_XONE, FF_MPV_OPT_FLAGS, "motion_est" },   \
{ "zero", NULL, 0, AV_OPT_TYPE_CONST, { .i64 = FF_ME_ZERO }, 0, 0, FF_MPV_OPT_FLAGS, "motion_est" }, \
{ "epzs", NULL, 0, AV_OPT_TYPE_CONST, { .i64 = FF_ME_EPZS }, 0, 0, FF_MPV_OPT_FLAGS, "motion_est" }, \
{ "xone", NULL, 0, AV_OPT_TYPE_CONST, { .i64 = FF_ME_XONE }, 0, 0, FF_MPV_OPT_FLAGS, "motion_est" }, \
{"b_strategy", "Strategy to choose between I/P/B-frames",           FF_MPV_OFFSET(b_frame_strategy), AV_OPT_TYPE_INT, {.i64 = 0 }, 0, 2, FF_MPV_OPT_FLAGS }, \
{"b_sensitivity", "Adjust sensitivity of b_frame_strategy 1",       FF_MPV_OFFSET(b_sensitivity), AV_OPT_TYPE_INT, {.i64 = 40 }, 1, INT_MAX, FF_MPV_OPT_FLAGS }, \
{"brd_scale", "Downscale frames for dynamic B-frame decision",      FF_MPV_OFFSET(brd_scale), AV_OPT_TYPE_INT, {.i64 = 0 }, 0, 3, FF_MPV_OPT_FLAGS }, \
{"skip_threshold", "Frame skip threshold",                          FF_MPV_OFFSET(frame_skip_threshold), AV_OPT_TYPE_INT, {.i64 = 0 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS }, \
{"skip_factor", "Frame skip factor",                                FF_MPV_OFFSET(frame_skip_factor), AV_OPT_TYPE_INT, {.i64 = 0 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS }, \
{"skip_exp", "Frame skip exponent",                                 FF_MPV_OFFSET(frame_skip_exp), AV_OPT_TYPE_INT, {.i64 = 0 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS }, \
{"skip_cmp", "Frame skip compare function",                         FF_MPV_OFFSET(frame_skip_cmp), AV_OPT_TYPE_INT, {.i64 = FF_CMP_DCTMAX }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS, "cmp_func" }, \
{"sc_threshold", "Scene change threshold",                          FF_MPV_OFFSET(scenechange_threshold), AV_OPT_TYPE_INT, {.i64 = 0 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS }, \
{"noise_reduction", "Noise reduction",                              FF_MPV_OFFSET(noise_reduction), AV_OPT_TYPE_INT, {.i64 = 0 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS }, \
{"mpeg_quant", "Use MPEG quantizers instead of H.263",              FF_MPV_OFFSET(mpeg_quant), AV_OPT_TYPE_INT, {.i64 = 0 }, 0, 1, FF_MPV_OPT_FLAGS }, \
{"ps", "RTP payload size in bytes",                             FF_MPV_OFFSET(rtp_payload_size), AV_OPT_TYPE_INT, {.i64 = 0 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS }, \
{"mepc", "Motion estimation bitrate penalty compensation (1.0 = 256)", FF_MPV_OFFSET(me_penalty_compensation), AV_OPT_TYPE_INT, {.i64 = 256 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS }, \
{"mepre", "pre motion estimation", FF_MPV_OFFSET(me_pre), AV_OPT_TYPE_INT, {.i64 = 0 }, INT_MIN, INT_MAX, FF_MPV_OPT_FLAGS }, \