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Thread: Video Recompression

  1. #1
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    Question Video Recompression

    Dear Encode.ru: I need some help, please....
    I have this set of videos (~12gb) in my tablet (Android 4.4) They weight too much and leave no room for anything else, so I decided to transcode them.
    Since I know nearly zero of video codecs, I want you to tell me, please, if there is a proved good codec to start with... h265 perhaps?
    I know there is no perfect solution. And i do *not* want to batch a billion permutations to brute-force the very best result. I am happy with a decent reduction in size while quality is preserved.
    The videos are half in .avi (mp4) and half in .m4v (avc), according to MediaInfo...
    They have no audio inside (sign language).

    So... What do you think??? Thanks in advance! Best Regards.
    Last edited by Gonzalo; 18th June 2015 at 00:21.

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    In my opinion, H.264 is good at size while quality is ok. I don't encode video for a while, so I don't hear anything about H.265. Just try both, or H.264 if you don't have time

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    h.264 / h.265 / webm /daala

    if you already have mp4-files and AVC-files then maybe H.264 would not improve the compression rate as it maybe use identically codecs

    "MP4 / Part 10" = "ISO/IEC 14496-10" introduce AVC = "Advanced Video Coding" = "a compression format for video signals which is technically identical to the ITU-T H.264 standard"

    H.265 can improve the compression rate - "40-50% bit rate reduction compared with H.264 at the same visual quality"

    http://www.extremetech.com/computing...o-expectations

    but
    http://www.streamingmedia.com/Articl...ct-102124.aspx

    ... definitely higher utilization of the CPU for x265- versus x264-encoded footage.
    ... all using VLC…It would average about 15 percent of the load at a 1080p source.
    ... That CPU use is sure to effect battery performance: "The hotter your CPU is running, the more you're going to drain that battery over time."

    for h.264 many devices can do HD Video Playback with Hardware H.264 Decoding

    in the future may be webm/VP9 or daala can be a alternative:

    http://www.trustedreviews.com/opinio...odes-explained
    http://www.xiph.org/daala/

    in short for now:

    - h.265 will improve compression rate, but has other/higher hardware requirements - the battery of your tablet will be shorter empty
    - h.264 can improve compression rate , if the content within your avi-container-files is coded with older codecs - you should try it

    maybe you can quickly reduce the necessary disc space with cutting

    - http://www.freemake.com/how_to/how_to_cut_video_quickly
    - http://www.solveigmm.com/en/products/avi-trimmer-mkv/
    - http://www.brizsoft.com/avisplit/

    best regards
    Attached Files Attached Files
    Last edited by joerg; 18th June 2015 at 11:19.

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    So sad it can be given only one "thanks" per post

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    Quote Originally Posted by joerg View Post
    if you already have mp4-files and AVC-files then maybe H.264 would not improve the compression rate as it maybe use identically codecs
    Actually, this is not true. Of course you can recompress the same video with the same codec and gain compression. You just have to accept a lower quality. This is also called "requantization". Whether the lower quality is acceptable for the OP is still to be seen.
    Quote Originally Posted by joerg View Post
    H.265 can improve the compression rate - "40-50% bit rate reduction compared with H.264 at the same visual quality"
    This gain factor is very much content dependent. For large content (large frame sizes) it might be true. For typical smaller size content, the gain is smaller, so do not expect miracles.
    Quote Originally Posted by joerg View Post
    ... definitely higher utilization of the CPU for x265- versus x264-encoded footage. ... all using VLC…It would average about 15 percent of the load at a 1080p source. ... That CPU use is sure to effect battery performance: "The hotter your CPU is running, the more you're going to drain that battery over time."
    Maybe. This depends highly how the encoder is configured. H.265 is optimized towards parallelization, so depending on the hardware, it might even be faster. However, typical (recent) hardware on smart phones may implement H.264 in hardware, and this is of course more efficient than to decode it on the CPU. This (the current) generation of hardware does of course not have H.265 implemented (obviously), so it is not so easy to compare.
    Quote Originally Posted by joerg View Post
    in the future may be webm/VP9 or daala can be a alternative:
    Depending on whom you trust. VP9 is probably better tuned towards web content (small images, lousy quality) whereas HEVC (h.265) is more tuned towards large frame sizes, so it is not so easy to give an affirmative answer which is better. As always "it depends".
    Quote Originally Posted by joerg View Post
    - h.265 will improve compression rate, but has other/higher hardware requirements - the battery of your tablet will be shorter empty
    Not necessarily. Unlike former MPEG standards, the complexity increase from AVC to HEVC is rather mild, if not even absent. It is just optimized for another goal.

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    thorfdbg you are right:

    if you can accept a lower quality (as an example not 1920x1080 but only 960x540 - the visible result naturally depends from the screen-resolution of the tablet)

    then of course we can significantly reduce the necessary disc space too.

    But this new encoding process can be a time-consuming process and if you are ready then you must decide if the resulting quality is good enough for you requirements.

    best regards

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    from personal test of of h.264 vs h.265 in a highly subjective, no objective metrics way, i couldnt see much different in what bitrate i was already using (800kbits to 1200kbits). howevere when i started dropping the bitrate down to 500kbits and 256kbits. there was huge different in 1080p content the h.264 started to look like old mpeg2 internet vidoes where as the h.265 retained quality similar to divx days aka mpeg4 ASP.

    so if you are gong to drop down to low bitrates i will defiantly recommending going with h.265 if you playback system can hadle it,
    my h.264 settings from hand brake : threads=2:rc-lookahead=60:ref=6:bframes=16:b-adapt=2:direct=auto:me=umh:subme=10:merange=24:ana lyse=all:trellis=2
    in h.265 i just selected the slow preset

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