Make videos more reproducible

[cobito]

Hello. I'm editing some videos and I'm having some trouble playing them back. They're encoded in x264 at 1080p and 25 Mbps. The problem is that there are parts with a lot of detail and it makes it play choppy. Even using video acceleration on the company's PC#1, when it gets to certain points, the video jumps around with CPU usage below 10%. When I play it back on a Popcorn Hour A110 the result is even worse than on the PC with hardware decoding. I've lowered the bitrate to 12 Mbps and the PC plays it back correctly, but the Popcorn still has issues. Finally I've reduced it to 720p while keeping it at 12 Mbps, but the Popcorn is still having the same issues (always in the same scene). Do you know what parameters I can modify to get smooth playback on all devices? For example, the High 5.1 or 4.1 profile, which I don't fully understand what it is, how would it help? I'd like to keep the bitrate as high as possible. Thanks.

[Sylver]

Hello cobito. I don't understand much about this, but based on the little experience of compressing movies to watch them on the PSP, you could lower the audio quality, which if it's not much to assume, must be that High 5.1 profile, that would also help to smooth out the weight and load for the player.

It's strange that at 720p and 12Mbps you can't move it fluently on your PC, you might need a better codec update or you just need to clean the S.O.

I personally watch movies at that medium detail on the PC4 (Athlon64 s754 at 2Ghz + Geforce FX 5500 256Mb AGP, on Win XP) and they go perfectly, but because the S.O. is immaculate, only intended to play movies in the living room, and with all possible codecs installed.

Regards

[cobito]

At 12 Mbps it runs smoothly on the PC. The problem comes in a couple of scenes where there is a lot of detail. The rest of the video looks good even at 25 Mbps on both the PC and the Popcorn.

[Sylver]

Well it's strange... I remember that it happened to me with more basic graphics, in some scenes with many effects and movements it did get stuck, but now it doesn't and I suppose that for you, due to graphic power, it shouldn't happen either. Apart from trying it on a clean Windows installation, the only thing I can think of is for you to download the latest codec pack if you don't have it yet, or even change the final format of the video. The desperate measure would be to edit the video, cut out the conflicting scenes and lower the detail even more separately, and then rebuild the movie, but I don't think anyone is up for that these days... Best regards

[MaxLG]

What graphics card do you use?

[cobito]

@MaxLG:

What graphics card do you use?

Geforce GTX 460 OC 1Gb.

The company's PC#1.

[MaxLG]

How strange,
have you tried overclocking the graphics card a little? A few Mhz more?

[hAyO]

The OC I don't think it will influence anything, I'm with Sylver, it will be a matter of codecs and stuff, I currently use a very similar combination of equipment, only the graphics change and honestly, zero problems.

[cobito]

Well, after doing a lot of tests I have discovered the problem.

The thing is that h264 is a format that has a bit of trouble maintaining a constant bit rate. When it is set to encode, for example, at 12 Mbps, this value is approximately the average bits per second of the entire video.

With the tests I have done, with a file encoded at 16 Mbps, in some very detailed scenes peaks of more than 50 Mbps are reached, an absolutely enormous rate and impossible for any hardware.

What needs to be done is just to limit the maximum bps so that the worst scenes do not exceed that rate. As I said before, h264 is a bit rebellious so there will always be fluctuations, but by playing with the different encoding parameters reasonable values are reached.

In my case I have managed to make the same video that exceeded 50 Mbps remain relatively constant between 20 and 30 mbps, something that is acceptable for the decoder of the graphics card and the popcorn hour without skimping on quality.

[Sylver]

Well done, little buddy, you have really delved into the issue. Very valuable information, I'll take note of it and formulate a question:
Does it affect the final size of the file? If so, it would be very useful for PSP videos and others.

Best regards!

[cobito]

@Sylver:

Bravo cobito, pues sí que has ahondado en la cuestión. Información muy valiosa, me la apunto y formulo cuestión:
¿repercute en el tamaño final del archivo? De ser así me conviene mucho para los videos de la PSP y demás.

Saludos!

En realidad eso depende de muchos parámetros. La mayoría de los programas que codifican en h264 te permiten elegir sólo el bitrate y el número de pasadas. Otros te permiten muchas más opciones. Por ejemplo con ffmpeg puedes elegir un bitrate máximo y mínimo además del medio y en Handbrake puedes elegir tan solo un bitrate máximo además del bitrate medio objetivo o bien un parámetro de calidad global. Si eliges un valor de calidad global determinado y limitas el bitrate máximo, en el caso de que tus videos tengan escenas complicadas (con mucho ruido, muchos detalles, mucho movimiento…), al limitar el bitrate máximo, harás que el video ocupe menos.

De todas formas en el aspecto del tamaño del archivo, aunque puedes ajustarlo un poco, estas configuraciones no son importantes. Si quieres que ocupe poco te sugiero esto: reduce la resolución a la resulución nativa del dispositivo, como método de decisión y predicción de subpíxeles elige una opción lenta (RD o QPRD).

Para una PSP (por ahí veo que tiene una resolución de 480x272), la tasa de bits puedes ajustarla mucho. Realmente no te puedo dar una cifra exacta.

Si tienes algo de tiempo libre y tienes un verdadero problema de espacio, te sugiero que hagas pruebas a 500, 1000, 1500, 2000... kbps, doble pasada, sin "terminaciones tempranas en el análisis de los subpixels", etc (la verdad es que es un mundo la leche de complejo de la cantidad de variables que se pueden elegir).

Los programas libres más completos que conozco en cuanto a configuraciones se refieren son ffmpeg y Handbrake. Este último tiene GUI, así que probablemente sea la opción más fácil.

Además también hay una componente subjetiva en este asunto: yo soy un tiquismisquis con la calidad y he necesitado codificar mi video a una media de 25 Mbps para que me guste el resultado. Otros con 8 o 10 Mbps hubieran tenido suficiente. Hablo de HD 1080p. En tu caso las tasas de bits bajarían bastante.

[Sylver]

Thank you very much, I knew a little in general, but not nearly as much. Now I will optimize the space much better :sisi:

Best regards