When I check audio bitrate of my video via OS file details, media players or ffprobe -i my_video.mp4, I get the bitrate is 128 kbps. And I want to get more detailed meta information of the video by ffprobe -loglevel 0 -print_format json -show_format -show_streams my_video.mp4. However audio bitrate value of the output is 128615 bps.
I thought it should be 128000 not 128615. Or 128 x 1024 = 131072. I wonder why it is not one of the values that I assumed. Also how can I safely say that this 128615 bps is 128 kbps?
Below is the detailed meta information for my video.
{
"streams": [
{
"index": 0,
"codec_name": "aac",
"codec_long_name": "AAC (Advanced Audio Coding)",
"profile": "LC",
"codec_type": "audio",
"codec_tag_string": "mp4a",
"codec_tag": "0x6134706d",
"sample_fmt": "fltp",
"sample_rate": "48000",
"channels": 2,
"channel_layout": "stereo",
"bits_per_sample": 0,
"initial_padding": 0,
"id": "0x1",
"r_frame_rate": "0/0",
"avg_frame_rate": "0/0",
"time_base": "1/48000",
"start_pts": 0,
"start_time": "0.000000",
"duration_ts": 965760,
"duration": "20.120000",
"bit_rate": "128615",
"nb_frames": "946",
"extradata_size": 2,
"disposition": {
"default": 1,
"dub": 0,
"original": 0,
"comment": 0,
"lyrics": 0,
"karaoke": 0,
"forced": 0,
"hearing_impaired": 0,
"visual_impaired": 0,
"clean_effects": 0,
"attached_pic": 0,
"timed_thumbnails": 0,
"captions": 0,
"descriptions": 0,
"metadata": 0,
"dependent": 0,
"still_image": 0
},
"tags": {
"creation_time": "2023-02-20T09:00:58.000000Z",
"language": "deu",
"handler_name": "Core Media Audio",
"vendor_id": "[0][0][0][0]"
}
},
{
"index": 1,
"codec_name": "h264",
"codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
"profile": "High",
"codec_type": "video",
"codec_tag_string": "avc1",
"codec_tag": "0x31637661",
"width": 1080,
"height": 1920,
"coded_width": 1080,
"coded_height": 1920,
"closed_captions": 0,
"film_grain": 0,
"has_b_frames": 0,
"sample_aspect_ratio": "1:1",
"display_aspect_ratio": "9:16",
"pix_fmt": "yuv420p",
"level": 42,
"color_range": "tv",
"color_space": "bt709",
"color_transfer": "bt709",
"color_primaries": "bt709",
"chroma_location": "left",
"field_order": "progressive",
"refs": 1,
"is_avc": "true",
"nal_length_size": "4",
"id": "0x2",
"r_frame_rate": "50/1",
"avg_frame_rate": "50/1",
"time_base": "1/50000",
"start_pts": 0,
"start_time": "0.000000",
"duration_ts": 1006000,
"duration": "20.120000",
"bit_rate": "20958903",
"bits_per_raw_sample": "8",
"nb_frames": "1006",
"extradata_size": 35,
"disposition": {
"default": 1,
"dub": 0,
"original": 0,
"comment": 0,
"lyrics": 0,
"karaoke": 0,
"forced": 0,
"hearing_impaired": 0,
"visual_impaired": 0,
"clean_effects": 0,
"attached_pic": 0,
"timed_thumbnails": 0,
"captions": 0,
"descriptions": 0,
"metadata": 0,
"dependent": 0,
"still_image": 0
},
"tags": {
"creation_time": "2023-02-20T09:00:58.000000Z",
"language": "und",
"handler_name": "Core Media Video",
"vendor_id": "[0][0][0][0]"
}
}
],
"format": {
"filename": "my_video.mp4",
"nb_streams": 2,
"nb_programs": 0,
"format_name": "mov,mp4,m4a,3gp,3g2,mj2",
"format_long_name": "QuickTime / MOV",
"start_time": "0.000000",
"duration": "20.120000",
"size": "53309460",
"bit_rate": "21196604",
"probe_score": 100,
"tags": {
"major_brand": "mp42",
"minor_version": "1",
"compatible_brands": "isommp41mp42",
"creation_time": "2023-02-20T09:00:58.000000Z"
}
}
}
I checked 1 kbps is 1000 bps and assumed 128 kbps of the audio bitrate should be 128000 bps. But it is 128615 bps when I run ffprobe.
