问题：
在我的例子中，比特流来自h264编码器，它是由现场摄像机提供的。比特流通过live555库使用RTSP协议发送。RTSP数据包由RTSP客户端接收，如vlc播放器（最重要的）、图腾播放器、mplayer。我需要知道如何设置较低的帧速率，因为我的相机产生9帧/秒的帧速，但大多数RTSP客户端都期望默认为25帧/秒，这会导致视频流无法正常播放（缓冲、丢弃延迟数据包等）。
问题：
我想知道RTSP客户端（播放软件）是如何从比特流中读取（或评估）帧率的。这些信息存储在哪里，如何发送到播放软件？
更多信息：
我使用的是live555中的testOnDemandRTSPServer示例代码。我已经从live555lib中编写了DeviceSource类的实现。我已经正确设置了演示时间：
gettimeofday(&fPresentationTime, NULL);
fDurationInMicroseconds = 1100000;
序列参数集NAL还包含适当的定时信息：
timing_info_present_flag : 1
num_units_in_tick : 1001
time_scale : 9000
fixed_frame_rate_flag : 1
RTSP标头包含帧速率：
a=framerate:9.0
不幸的是，这无济于事。我认为视频播放器将平静地等待新的帧，并且帧速率将和接收另一个RTP分组（另一个NAL）的频率相关。
视频播放器的行为：
VLC播放器-视频是不稳定的，因为VLC预计下一帧会更早（25帧而不是9帧）。结果，vlc将缓冲时间增加到例如10s，在此期间视频被冻结。
图腾玩家-SPS Nal的计时信息由图腾解析。帧速率显示正常，但视频仍不稳定（延迟约500ms）。它似乎在等待更多的帧（每秒25帧）。
Mplayer识别出错误的帧速率值，显示每秒25帧，但视频非常流畅，质量良好：
mplayer ffmpeg://rtsp://192.168.1.82:8554/testStream
.
.
.
VIDEO: [H264] 320x240 0bpp 25.000 fps 0.0 kbps ( 0.0 kbyte/s)
Live555 RTSP客户端测试应用程序./live555/testProgs/testRTSPClientrtsp://192.168.1.82:8554/testStream
Opening connection to 192.168.1.82, port 8554...
...remote connection opened
Sending request: DESCRIBE rtsp://192.168.1.82:8554/testStream RTSP/1.0
CSeq: 2
User-Agent: ./testRTSPClient (LIVE555 Streaming Media v2016.02.22)
Accept: application/sdp
Received 675 new bytes of response data.
Received a complete DESCRIBE response:
RTSP/1.0 200 OK
CSeq: 2
Date: Fri, Jan 01 1988 00:00:23 GMT
Content-Base: rtsp://192.168.1.82:8554/testStream/
Content-Type: application/sdp
Content-Length: 506
v=0
o=- 567993603275971 1 IN IP4 192.168.1.82
s=Session streamed by "testOnDemandRTSPServer"
i=testStream
t=0 0
a=tool:LIVE555 Streaming Media v2016.02.22
a=type:broadcast
a=control:*
a=range:npt=0-
a=x-qt-text-nam:Session streamed by "testOnDemandRTSPServer"
a=x-qt-text-inf:testStream
m=video 0 RTP/AVP 96
c=IN IP4 0.0.0.0
b=AS:500
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1;profile-level-id=42801E;sprop-parameter-sets=Z0KAHpWgUHxA,aM44gA==
a=framerate:9.0
a=control:track1
[URL:"rtsp://192.168.1.82:8554/testStream/"]: Got a SDP description:
v=0
o=- 567993603275971 1 IN IP4 192.168.1.82
s=Session streamed by "testOnDemandRTSPServer"
i=testStream
t=0 0
a=tool:LIVE555 Streaming Media v2016.02.22
a=type:broadcast
a=control:*
a=range:npt=0-
a=x-qt-text-nam:Session streamed by "testOnDemandRTSPServer"
a=x-qt-text-inf:testStream
m=video 0 RTP/AVP 96
c=IN IP4 0.0.0.0
b=AS:500
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1;profile-level-id=42801E;sprop-parameter-sets=Z0KAHpWgUHxA,aM44gA==
a=framerate:9.0
a=control:track1
[URL:"rtsp://192.168.1.82:8554/testStream/"]: Initiated the "video/H264" subsession (client ports 57660-57661)
Sending request: SETUP rtsp://192.168.1.82:8554/testStream/track1 RTSP/1.0
CSeq: 3
User-Agent: ./testRTSPClient (LIVE555 Streaming Media v2016.02.22)
Transport: RTP/AVP;unicast;client_port=57660-57661
Received 215 new bytes of response data.
Received a complete SETUP response:
RTSP/1.0 200 OK
CSeq: 3
Date: Fri, Jan 01 1988 00:00:23 GMT
Transport: RTP/AVP;unicast;destination=192.168.1.109;source=192.168.1.82;client_port=57660-57661;server_port=6970-6971
Session: 06B1DFA4;timeout=65
[URL:"rtsp://192.168.1.82:8554/testStream/"]: Set up the "video/H264" subsession (client ports 57660-57661)
[URL:"rtsp://192.168.1.82:8554/testStream/"]: Created a data sink for the "video/H264" subsession
Sending request: PLAY rtsp://192.168.1.82:8554/testStream/ RTSP/1.0
CSeq: 4
User-Agent: ./testRTSPClient (LIVE555 Streaming Media v2016.02.22)
Session: 06B1DFA4
Range: npt=0.000-
Received 96 new bytes of response data.
Received 94 new bytes of response data.
Received a complete PLAY response:
RTSP/1.0 200 OK
CSeq: 4
Date: Fri, Jan 01 1988 00:00:23 GMT
Range: npt=0.000-
Session: 06B1DFA4
RTP-Info: url=rtsp://192.168.1.82:8554/testStream/track1;seq=52833;rtptime=3161001994
[URL:"rtsp://192.168.1.82:8554/testStream/"]: Started playing session...
Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received 10874 bytes. Presentation time: 567993623.442288
Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received 12054 bytes. Presentation time: 567993623.482288
Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received 12227 bytes. Presentation time: 567993623.522288
Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received 12281 bytes. Presentation time: 567993623.562288
Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received 12384 bytes. Presentation time: 567993623.602288
Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received 12129 bytes. Presentation time: 567993623.642288
Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received 12141 bytes. Presentation time: 567993623.682288
Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received 12287 bytes. Presentation time: 567993623.722288
Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received 16415 bytes. Presentation time: 567993623.762288
Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received 12360 bytes. Presentation time: 567993623.802288
Stream "rtsp://192.168.1.82:8554/testStream/"; video/H264: Received 12167 bytes. Presentation time: 567993623.842288
我通过工具h264_analyze解析了我的NAL，下面是输出（只有几个第一个NAL）：
!! Found NAL at offset 4 (0x0004), size 18 (0x0012)
XX 00 00 00 01 67 42 80 1E 95 A0 50 7C 84 00 00 0F
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 3
nal_unit_type : 7 ( Sequence parameter set )
======= SPS =======
profile_idc : 66
constraint_set0_flag : 1
constraint_set1_flag : 0
constraint_set2_flag : 0
constraint_set3_flag : 0
constraint_set4_flag : 0
constraint_set5_flag : 0
reserved_zero_2bits : 0
level_idc : 30
seq_parameter_set_id : 0
chroma_format_idc : 1
residual_colour_transform_flag : 0
bit_depth_luma_minus8 : 0
bit_depth_chroma_minus8 : 0
qpprime_y_zero_transform_bypass_flag : 0
seq_scaling_matrix_present_flag : 0
log2_max_frame_num_minus4 : 4
pic_order_cnt_type : 2
log2_max_pic_order_cnt_lsb_minus4 : 0
delta_pic_order_always_zero_flag : 0
offset_for_non_ref_pic : 0
offset_for_top_to_bottom_field : 0
num_ref_frames_in_pic_order_cnt_cycle : 0
num_ref_frames : 1
gaps_in_frame_num_value_allowed_flag : 0
pic_width_in_mbs_minus1 : 19
pic_height_in_map_units_minus1 : 14
frame_mbs_only_flag : 1
mb_adaptive_frame_field_flag : 0
direct_8x8_inference_flag : 0
frame_cropping_flag : 0
frame_crop_left_offset : 0
frame_crop_right_offset : 0
frame_crop_top_offset : 0
frame_crop_bottom_offset : 0
vui_parameters_present_flag : 1
=== VUI ===
aspect_ratio_info_present_flag : 0
aspect_ratio_idc : 0
sar_width : 0
sar_height : 0
overscan_info_present_flag : 0
overscan_appropriate_flag : 0
video_signal_type_present_flag : 0
video_format : 0
video_full_range_flag : 0
colour_description_present_flag : 0
colour_primaries : 0
transfer_characteristics : 0
matrix_coefficients : 0
chroma_loc_info_present_flag : 0
chroma_sample_loc_type_top_field : 0
chroma_sample_loc_type_bottom_field : 0
timing_info_present_flag : 1
num_units_in_tick : 1001
time_scale : 9000
fixed_frame_rate_flag : 1
nal_hrd_parameters_present_flag : 0
vcl_hrd_parameters_present_flag : 0
low_delay_hrd_flag : 0
pic_struct_present_flag : 0
bitstream_restriction_flag : 0
motion_vectors_over_pic_boundaries_flag : 0
max_bytes_per_pic_denom : 0
max_bits_per_mb_denom : 0
log2_max_mv_length_horizontal : 0
log2_max_mv_length_vertical : 0
num_reorder_frames : 0
max_dec_frame_buffering : 0
=== HRD ===
cpb_cnt_minus1 : 0
bit_rate_scale : 0
cpb_size_scale : 0
bit_rate_value_minus1[0] : 0
cpb_size_value_minus1[0] : 0
cbr_flag[0] : 0
initial_cpb_removal_delay_length_minus1 : 0
cpb_removal_delay_length_minus1 : 0
dpb_output_delay_length_minus1 : 0
time_offset_length : 0
!! Found NAL at offset 26 (0x001A), size 4 (0x0004)
XX 00 00 00 01 68 CE 38 80
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 3
nal_unit_type : 8 ( Picture parameter set )
======= PPS =======
pic_parameter_set_id : 0
seq_parameter_set_id : 0
entropy_coding_mode_flag : 0
pic_order_present_flag : 0
num_slice_groups_minus1 : 0
slice_group_map_type : 0
num_ref_idx_l0_active_minus1 : 0
num_ref_idx_l1_active_minus1 : 0
weighted_pred_flag : 0
weighted_bipred_idc : 0
pic_init_qp_minus26 : 0
pic_init_qs_minus26 : 0
chroma_qp_index_offset : 0
deblocking_filter_control_present_flag : 0
constrained_intra_pred_flag : 0
redundant_pic_cnt_present_flag : 0
transform_8x8_mode_flag : 0
pic_scaling_matrix_present_flag : 0
second_chroma_qp_index_offset : 0
!! Found NAL at offset 33 (0x0021), size 339 (0x0153)
XX 80 00 00 01 65 B8 04 04 3F FF F8 7A 28 03 EF BE
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 3
nal_unit_type : 5 ( Coded slice of an IDR picture )
======= Slice Header =======
first_mb_in_slice : 0
slice_type : 2 ( I slice )
pic_parameter_set_id : 0
frame_num : 0
field_pic_flag : 0
bottom_field_flag : 0
idr_pic_id : 0
pic_order_cnt_lsb : 0
delta_pic_order_cnt_bottom : 0
redundant_pic_cnt : 0
direct_spatial_mv_pred_flag : 0
num_ref_idx_active_override_flag : 0
num_ref_idx_l0_active_minus1 : 0
num_ref_idx_l1_active_minus1 : 0
cabac_init_idc : 0
slice_qp_delta : -16
sp_for_switch_flag : 0
slice_qs_delta : 0
disable_deblocking_filter_idc : 0
slice_alpha_c0_offset_div2 : 0
slice_beta_offset_div2 : 0
slice_group_change_cycle : 0
=== Prediction Weight Table ===
luma_log2_weight_denom : 0
chroma_log2_weight_denom : 0
=== Ref Pic List Reordering ===
ref_pic_list_reordering_flag_l0 : 0
ref_pic_list_reordering_flag_l1 : 0
=== Decoded Ref Pic Marking ===
no_output_of_prior_pics_flag : 0
long_term_reference_flag : 0
adaptive_ref_pic_marking_mode_flag : 0
!! Found NAL at offset 376 (0x0178), size 1897 (0x0769)
XX 00 00 00 01 41 E0 20 3F 36 5F FF 87 A2 80 03 7E
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 2
nal_unit_type : 1 ( Coded slice of a non-IDR picture )
======= Slice Header =======
first_mb_in_slice : 0
slice_type : 0 ( P slice )
pic_parameter_set_id : 0
frame_num : 1
field_pic_flag : 0
bottom_field_flag : 0
idr_pic_id : 0
pic_order_cnt_lsb : 0
delta_pic_order_cnt_bottom : 0
redundant_pic_cnt : 0
direct_spatial_mv_pred_flag : 0
num_ref_idx_active_override_flag : 0
num_ref_idx_l0_active_minus1 : 0
num_ref_idx_l1_active_minus1 : 0
cabac_init_idc : 0
slice_qp_delta : -15
sp_for_switch_flag : 0
slice_qs_delta : 0
disable_deblocking_filter_idc : 0
slice_alpha_c0_offset_div2 : 0
slice_beta_offset_div2 : 0
slice_group_change_cycle : 0
=== Prediction Weight Table ===
luma_log2_weight_denom : 0
chroma_log2_weight_denom : 0
=== Ref Pic List Reordering ===
ref_pic_list_reordering_flag_l0 : 0
ref_pic_list_reordering_flag_l1 : 0
=== Decoded Ref Pic Marking ===
no_output_of_prior_pics_flag : 0
long_term_reference_flag : 0
adaptive_ref_pic_marking_mode_flag : 0
!! Found NAL at offset 2277 (0x08E5), size 2989 (0x0BAD)
XX 00 00 00 01 41 E0 40 3F 37 0F 0C 3E D8 A0 00 4E
==================== NAL ====================
forbidden_zero_bit : 0
nal_ref_idc : 2
nal_unit_type : 1 ( Coded slice of a non-IDR picture )
======= Slice Header =======
first_mb_in_slice : 0
slice_type : 0 ( P slice )
pic_parameter_set_id : 0
frame_num : 2
field_pic_flag : 0
bottom_field_flag : 0
idr_pic_id : 0
pic_order_cnt_lsb : 0
delta_pic_order_cnt_bottom : 0
redundant_pic_cnt : 0
direct_spatial_mv_pred_flag : 0
num_ref_idx_active_override_flag : 0
num_ref_idx_l0_active_minus1 : 0
num_ref_idx_l1_active_minus1 : 0
cabac_init_idc : 0
slice_qp_delta : -15
sp_for_switch_flag : 0
slice_qs_delta : 0
disable_deblocking_filter_idc : 0
slice_alpha_c0_offset_div2 : 0
slice_beta_offset_div2 : 0
slice_group_change_cycle : 0
=== Prediction Weight Table ===
luma_log2_weight_denom : 0
chroma_log2_weight_denom : 0
=== Ref Pic List Reordering ===
ref_pic_list_reordering_flag_l0 : 0
ref_pic_list_reordering_flag_l1 : 0
=== Decoded Ref Pic Marking ===
no_output_of_prior_pics_flag : 0
long_term_reference_flag : 0
adaptive_ref_pic_marking_mode_flag : 0
!! Found NAL at offset 5270 (0x1496), size 4074 (0x0FEA)
XX 00 00 00 01 41 E0 60 10 CD B7 C1 BF B8 36 00 6A
我想知道RTSP客户端（播放软件）是如何从比特流中读取（或评估）帧率的。这些信息存储在哪里，如何发送到播放软件？
客户端不需要知道播放接收到的视频的帧速率。播放是根据RTP和NTP时间戳计算的呈现时间进行的。
流"；rtsp://192.168.1.82:8554/testStream/"；video/H264：已接收10874字节。展示时间：567993623.442288
流"；rtsp://192.168.1.82:8554/testStream/"；video/H264：接收12054字节。展示时间：567993623.482288
您似乎没有正确设置演示时间。这可能是你每秒25帧的速度。如果设置正确，testRTSPClient将每秒打印9个样本，它们之间的差异大约为1/9秒。你的差异大约是40毫秒，给你25帧/秒。
a=帧速率：9.0
我已经开发了使用各种帧速率内容的RTSP服务器，并且从未需要设置SDP属性。我不确定是什么客户端软件真正利用了它
VLC播放器-视频是不稳定的，因为VLC预计下一帧会更早（25帧而不是9帧）。结果，vlc将缓冲时间增加到例如10s，在此期间视频被冻结。
根据我过去几年的经验，VLC不擅长回放现场内容。我测试过各种RTSP服务器，VLC经常遇到问题，即使在使用更大的网络抖动缓冲区时也是如此。
你可能想看看其他一些东西：
fDurationInMicroseconds=1100000；
如注释中所述，对于实时源，fDurationInMicroseconds应设置为0。
b=AS:500
比特率似乎设置错误：您的流绝对不是500kbps。
问题已解决。我在流媒体上使用了错误的类。此处描述：http://lists.live555.com/pipermail/live-devel/2016-April/020013.html
根据Ross的提示，我将H264VideoStreamFramer替换为H264VideoStreamDiscreteFramer，并从NAL单元中删除了起始代码。现在一切都很顺利。