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Perhaps someone here can answer a question I've had for a while: if you stream a video which is actually a static image (think a song on YouTube, the 'video' is

Perhaps someone here can answer a question I've had for a while: if you stream a video which is actually a static image (think a song on YouTube, the 'video' is just the album cover) is there any way to optimise that? Or must the server stream that same image constantly as though it was a regular video?

knaik94 6y ago
That's optimized based on the video codec itself where you keep frames with major changes but surrounding frames can be optimized by encoding where certain pixels move. That's essentially what the bitrate tells us, how much of the bits are new and how many are copied from a previous frame. This is an oversimplification, but with static images, you would need a low bitrate after the initial few frames because it doesn't change. And bitrate is a proxy to how much data is transmitted while streaming, it's bits per second. So a more concise answer, the codecs used for video by YouTube have the optimization you're thinking about built in. It would send a "pixel didn't change from last frame" and not need to send all the color information for all the pixels. YouTube does not really do variable frame rate, and it's messy for editing, but it's another optimization that is possible and could be useful for the type of video you're describing. The article describes DASH which you would need to send the full frame initially every time segment but per segment the previously described concept still applies. I don't believe YouTube uses DASH for anything outside live streams.
rocgf 6y ago
I do not know the answer, but I would absolutely shocked if it was streamed as a regular video. To the best of my knowledge, there are many, many optimizations which go into video. This is a pretty good high-level video I came across - https://www.youtube.com/watch?v=r6Rp-uo6HmI https://www.youtube.com/watch?v=r6Rp-uo6HmI
- LocalH 6y ago
  I mean, technically, it would be "streamed as a regular video", it's just that "regular video encoding" is pretty efficient at encoding a single unchanging image nowadays.
zinekeller 6y ago
The previous answers were speculative, but I have tried to download a random audio/video that was uploaded through YouTube's media programme (directly by media companies), and the answer is that they do re-send the video frame every 5 seconds for both H.264 and VP9, and it is encoded both at a rate of 25 frames per second and the width and height are the same. Here are the file details for both formats: H.264/AAC4: Video ID : 1 Format : AVC Format/Info : Advanced Video Codec Format profile : High@L3.2 Format settings : CABAC / 2 Ref Frames Format settings, CABAC : Yes Format settings, Reference frames : 2 frames Codec ID : avc1 Codec ID/Info : Advanced Video Coding Duration : 3 min 29 s Bit rate : 375 kb/s Width : 1 080 pixels Height : 1 080 pixels Display aspect ratio : 1.000 Frame rate mode : Constant Frame rate : 25.000 FPS Color space : YUV Chroma subsampling : 4:2:0 Bit depth : 8 bits Scan type : Progressive Bits/(Pixel*Frame) : 0.013 Stream size : 9.35 MiB (74%) Writing library : x264 core 155 r2901 7d0ff22 Codec configuration box : avcC Audio ID : 2 Format : AAC LC Format/Info : Advanced Audio Codec Low Complexity Codec ID : mp4a-40-2 Duration : 3 min 29 s Bit rate mode : Constant Bit rate : 128 kb/s Channel(s) : 2 channels Channel layout : L R Sampling rate : 44.1 kHz Frame rate : 43.066 FPS (1024 SPF) Compression mode : Lossy Stream size : 3.19 MiB (25%) Default : Yes Alternate group : 1 VP9/Opus: Video ID : 1 Format : VP9 Codec ID : V_VP9 Duration : 3 min 29 s Width : 1 080 pixels Height : 1 080 pixels Display aspect ratio : 1.000 Frame rate mode : Constant Frame rate : 25.000 FPS Language : English Default : Yes Forced : No Color range : Limited Audio ID : 2 Format : Opus Codec ID : A_OPUS Duration : 3 min 29 s Channel(s) : 2 channels Channel layout : L R Sampling rate : 48.0 kHz Bit depth : 32 bits Compression mode : Lossy Language : English Default : Yes Forced : No

knaik94 6y ago

That's optimized based on the video codec itself where you keep frames with major changes but surrounding frames can be optimized by encoding where certain pixels move. That's essentially what the bitrate tells us, how much of the bits are new and how many are copied from a previous frame. This is an oversimplification, but with static images, you would need a low bitrate after the initial few frames because it doesn't change. And bitrate is a proxy to how much data is transmitted while streaming, it's bits per second. So a more concise answer, the codecs used for video by YouTube have the optimization you're thinking about built in. It would send a "pixel didn't change from last frame" and not need to send all the color information for all the pixels. YouTube does not really do variable frame rate, and it's messy for editing, but it's another optimization that is possible and could be useful for the type of video you're describing. The article describes DASH which you would need to send the full frame initially every time segment but per segment the previously described concept still applies. I don't believe YouTube uses DASH for anything outside live streams.

rocgf 6y ago

I do not know the answer, but I would absolutely shocked if it was streamed as a regular video. To the best of my knowledge, there are many, many optimizations which go into video. This is a pretty good high-level video I came across - https://www.youtube.com/watch?v=r6Rp-uo6HmI https://www.youtube.com/watch?v=r6Rp-uo6HmI

LocalH 6y ago
I mean, technically, it would be "streamed as a regular video", it's just that "regular video encoding" is pretty efficient at encoding a single unchanging image nowadays.

zinekeller 6y ago

The previous answers were speculative, but I have tried to download a random audio/video that was uploaded through YouTube's media programme (directly by media companies), and the answer is that they do re-send the video frame every 5 seconds for both H.264 and VP9, and it is encoded both at a rate of 25 frames per second and the width and height are the same. Here are the file details for both formats: H.264/AAC4: Video ID : 1 Format : AVC Format/Info : Advanced Video Codec Format profile : High@L3.2 Format settings : CABAC / 2 Ref Frames Format settings, CABAC : Yes Format settings, Reference frames : 2 frames Codec ID : avc1 Codec ID/Info : Advanced Video Coding Duration : 3 min 29 s Bit rate : 375 kb/s Width : 1 080 pixels Height : 1 080 pixels Display aspect ratio : 1.000 Frame rate mode : Constant Frame rate : 25.000 FPS Color space : YUV Chroma subsampling : 4:2:0 Bit depth : 8 bits Scan type : Progressive Bits/(Pixel*Frame) : 0.013 Stream size : 9.35 MiB (74%) Writing library : x264 core 155 r2901 7d0ff22 Codec configuration box : avcC Audio ID : 2 Format : AAC LC Format/Info : Advanced Audio Codec Low Complexity Codec ID : mp4a-40-2 Duration : 3 min 29 s Bit rate mode : Constant Bit rate : 128 kb/s Channel(s) : 2 channels Channel layout : L R Sampling rate : 44.1 kHz Frame rate : 43.066 FPS (1024 SPF) Compression mode : Lossy Stream size : 3.19 MiB (25%) Default : Yes Alternate group : 1 VP9/Opus: Video ID : 1 Format : VP9 Codec ID : V_VP9 Duration : 3 min 29 s Width : 1 080 pixels Height : 1 080 pixels Display aspect ratio : 1.000 Frame rate mode : Constant Frame rate : 25.000 FPS Language : English Default : Yes Forced : No Color range : Limited Audio ID : 2 Format : Opus Codec ID : A_OPUS Duration : 3 min 29 s Channel(s) : 2 channels Channel layout : L R Sampling rate : 48.0 kHz Bit depth : 32 bits Compression mode : Lossy Language : English Default : Yes Forced : No